CSS 2025 – General Science & Ability – Complete Solution

Part I – Multiple Choice Questions (MCQs)

Marks: 20

Answers to MCQs

1. ‘Blue dwarfs’ and ‘Red giants’ respectively refer to:
Answer: (B) Young star and Old star
Blue dwarfs are young, hot stars while red giants are older, cooler stars in later stages of stellar evolution.
2. Most major Tsunamis are produced by earthquakes with hypocenters less than:
Answer: (A) 30 km
Shallow earthquakes (less than 30 km depth) are more effective at displacing water and generating tsunamis.
3. Which source of energy is caused by uneven heating of earth’s surface?
Answer: (A) Wind
Wind energy results from temperature differences causing air movement.
4. Global winds towards western direction are known as:
Answer: (B) Western winds
Westerlies blow from west to east in mid-latitudes.
5. Perinatal transmission occurs when a pathogen is transmitted from:
Answer: (C) Mother to infant
Perinatal transmission happens shortly before or after birth.
6. Which plant group needs both land and water to complete their life cycle?
Answer: (A) Bryophyta
Bryophytes (mosses) require water for reproduction but live on land.
7. Maximum amount of carbohydrates are obtained from:
Answer: (C) Whole grain food
Whole grains are rich sources of complex carbohydrates.
8. Which class has the largest number of animals?
Answer: (B) Insects
Insects represent the largest class in the animal kingdom with over 1 million described species.
9. The process of preserving meat by stewing in a covered earthenware jug is called:
Answer: (B) Jugging
Jugging is a traditional cooking method for game meats.
10. All operating systems get their total memory initialized from:
Answer: (A) BIOS
BIOS (Basic Input/Output System) initializes hardware during boot process.
11. The amount of data transmitted for a given amount of time is called:
Answer: (B) Bandwidth
Bandwidth measures data transmission capacity.
12. Which products can be prepared using raw guava?
Answer: (C) Both (A) and (B)
Guava can be used to make both jam and jelly.
13. Which is used as a stabilizer in ice cream?
Answer: (C) Gelatin
Gelatin helps prevent ice crystal formation in ice cream.
14. In fiber structure, light is guided through the core due to total internal:
Answer: (A) Reflection
Total internal reflection keeps light within the optical fiber core.
15. Who is known as the inventor of Artificial Intelligence?
Answer: (B) John McCarthy
John McCarthy coined the term “Artificial Intelligence” in 1956.
16. Which is the common language for Artificial Intelligence?
Answer: (C) Lisp
Lisp has been widely used in AI research since its inception.
17. Cement factory laborers are prone to:
Answer: (B) Cytosilicosis
Cytosilicosis is a lung disease caused by inhaling cement dust.
18. The fastest enzyme is:
Answer: (C) Carbonic anhydrase
Carbonic anhydrase can hydrate 1 million CO₂ molecules per second.
19. Process of adding vitamins to milk is known as:
Answer: (B) Fortification
Fortification adds nutrients to food products.
20. The waves used for line of sight (LOS) communication are called:
Answer: (A) Space waves
Space waves travel directly from transmitter to receiver in line of sight.

SECTION A – GENERAL SCIENCE

Q.2 Earth Rotation, Revolution & Environment

Marks: 20

(a) Effects of Earth’s Rotation and Revolution

Effects of Rotation (24-hour cycle):

  • Day and Night: Alternating periods of light and darkness
  • Coriolis Effect: Deflection of winds and ocean currents
  • Tides: Gravitational pull causing daily tidal cycles
  • Temperature Regulation: Prevents extreme temperature variations

Effects of Revolution (365-day cycle):

  • Seasons: Due to Earth’s axial tilt (23.5°) and orbital position
  • Variation in Day Length: Longer days in summer, shorter in winter
  • Seasonal Weather Patterns: Monsoons, seasonal temperature changes
  • Zodiac Constellations: Changing night sky throughout the year

(b) Electromagnetic Radiations

Electromagnetic radiation consists of waves of electric and magnetic fields propagating through space. They travel at speed of light (3×10⁸ m/s) and don’t require a medium.

Types and Applications:

Type Wavelength Range Applications
Radio Waves > 1 m Broadcasting, Communication, Radar
Microwaves 1 mm – 1 m Cooking, Satellite Communication, WiFi
Infrared 700 nm – 1 mm Remote Controls, Thermal Imaging, Heating
Visible Light 400-700 nm Vision, Photography, Fiber Optics
Ultraviolet 10-400 nm Sterilization, Vitamin D Production, Forensics
X-rays 0.01-10 nm Medical Imaging, Security Screening
Gamma Rays < 0.01 nm Cancer Treatment, Nuclear Medicine

(c) Hurricanes

Hurricanes are powerful tropical cyclones with sustained winds exceeding 74 mph (119 km/h).

Formation Process:

  1. Warm ocean waters (>26.5°C) provide energy
  2. Low pressure system develops over warm water
  3. Moist air rises, cools, and condenses releasing heat
  4. Coriolis effect causes rotation
  5. Organized thunderstorm activity forms spiral bands

Damage Levels:

  • Category 1 (74-95 mph): Minimal damage to vegetation
  • Category 2 (96-110 mph): Moderate damage to buildings
  • Category 3 (111-129 mph): Extensive damage, evacuation needed
  • Category 4 (130-156 mph): Catastrophic damage to structures
  • Category 5 (>157 mph): Complete destruction of buildings

(d) Nitrogen Fertilizers and Insecticides

Advantages of Nitrogen Fertilizers:

  • Increased crop yield and faster plant growth
  • Improved protein content in grains
  • Cost-effective and readily available
  • Easy application methods

Disadvantages of Nitrogen Fertilizers:

  • Water pollution through runoff causing eutrophication
  • Soil acidification and degradation
  • Greenhouse gas emissions (nitrous oxide)
  • Health risks from nitrate contamination in water

Advantages of Insecticides:

  • Effective pest control protecting crops
  • Increased agricultural productivity
  • Disease prevention (malaria, dengue control)
  • Cost-effective for large-scale farming

Disadvantages of Insecticides:

  • Harm to non-target species and biodiversity loss
  • Pesticide resistance development
  • Environmental persistence and bioaccumulation
  • Human health risks from exposure

Q.3 Photosynthesis, Circulatory System & Health

Marks: 20

(a) Temperature and Light Effects on Photosynthesis

Temperature Effects:

  • Low Temperature (0-10°C): Enzymatic activity slows, reducing photosynthesis rate
  • Optimal Range (20-30°C): Maximum photosynthetic efficiency
  • High Temperature (>35°C): Enzymes denature, stomata close, rate decreases
  • Extreme Heat (>45°C): Photosynthetic apparatus damaged

Light Intensity Effects:

  • Low Light: Photosynthesis limited by light availability
  • Light Compensation Point: Where photosynthesis equals respiration
  • Increasing Light: Linear increase in photosynthesis rate
  • Light Saturation: Maximum rate reached, other factors become limiting
  • Photoinhibition: Excessive light damages photosynthetic pigments

(b) Capillaries in Circulatory System

Structure:

  • Smallest blood vessels (5-10 μm diameter)
  • Single layer of endothelial cells
  • Thin walls for efficient exchange
  • Form extensive networks throughout tissues

Functions:

  • Nutrient Delivery: Transport oxygen, glucose, amino acids to tissues
  • Waste Removal: Carry away CO₂, metabolic wastes
  • Fluid Exchange: Maintain tissue fluid balance
  • Thermoregulation: Help control body temperature
  • Immune Function: Allow white blood cell migration

(c) Hepatitis

Hepatitis is inflammation of the liver, commonly caused by viral infection.

Types of Hepatitis:

  • Hepatitis A: Food/water borne, acute infection
  • Hepatitis B: Blood/body fluids, can become chronic
  • Hepatitis C: Blood transmission, often chronic
  • Hepatitis D: Requires Hepatitis B co-infection
  • Hepatitis E: Waterborne, similar to Hepatitis A

Common Symptoms:

  • Fatigue and weakness
  • Jaundice (yellowing of skin/eyes)
  • Dark urine and pale stools
  • Abdominal pain and nausea
  • Loss of appetite and weight loss

Preventions:

  • Vaccination (available for Hepatitis A and B)
  • Safe food and water practices
  • Proper hygiene and sanitation
  • Safe injection practices
  • Screening blood products
  • Protected sexual practices

(d) Biomass vs Biogas

Aspect Biomass Biogas
Definition Organic matter used as fuel Gaseous fuel produced from biomass
Form Solid, liquid, or gaseous Gaseous only
Composition Wood, crops, agricultural waste Methane (50-75%), CO₂, other gases
Production Direct combustion or processing Anaerobic digestion

Methods for Obtaining Energy from Biomass:

  1. Direct Combustion: Burning biomass to produce heat/electricity
  2. Gasification: Converting biomass to synthetic gas at high temperatures
  3. Pyrolysis: Thermal decomposition without oxygen to produce bio-oil
  4. Anaerobic Digestion: Microbial breakdown producing biogas
  5. Fermentation: Converting sugars to ethanol for biofuel
  6. Transesterification: Producing biodiesel from vegetable oils

Q.6 Mathematical Problems

Marks: 20

(a) Fridge and Freezer Price Calculation

Given:

  • Total paid after 15% discount: Rs. 57,120
  • Freezer original price: Rs. 40,000
  • Discount: 15% on everything

Solution:

Let the original price of fridge = x

Total original price = 40,000 + x

After 15% discount, paid amount = 85% of total original price

0.85 × (40,000 + x) = 57,120
40,000 + x = 57,120 ÷ 0.85
40,000 + x = 67,200
x = 67,200 – 40,000 = 27,200

Original price of fridge = Rs. 27,200

(b) Monthly Payment Calculation

Given:

  • Deposit: Rs. 60,000
  • 36 equal monthly payments
  • Total paid = 127% of basic price
  • Basic price: Rs. 3,360,000

Solution:

Total amount paid = 127% of 3,360,000

Total paid = 1.27 × 3,360,000 = 4,267,200

Amount paid through installments = Total – Deposit

Installment amount = 4,267,200 – 60,000 = 4,207,200

Monthly payment = Total installment amount ÷ 36

Monthly payment = 4,207,200 ÷ 36 = 116,866.67

Monthly payment = Rs. 116,866.67

(c) Division of Rs. 600 among A, B, C

Given:

Let A’s share = a, B’s share = b, C’s share = c

Total: a + b + c = 600

Conditions:

  • 40 + (2/5)a = (2/7)b + 20 = (9/17)c + 10

Solution:

Let the common value = k

40 + (2/5)a = k ⇒ a = (5/2)(k – 40)
20 + (2/7)b = k ⇒ b = (7/2)(k – 20)
10 + (9/17)c = k ⇒ c = (17/9)(k – 10)

Substitute in total equation:

(5/2)(k – 40) + (7/2)(k – 20) + (17/9)(k – 10) = 600

Multiply through by 18 to eliminate denominators:

45(k – 40) + 63(k – 20) + 34(k – 10) = 10,800
45k – 1800 + 63k – 1260 + 34k – 340 = 10,800
142k – 3400 = 10,800
142k = 14,200 ⇒ k = 100

Now calculate shares:

a = (5/2)(100 – 40) = (5/2)×60 = 150
b = (7/2)(100 – 20) = (7/2)×80 = 280
c = (17/9)(100 – 10) = (17/9)×90 = 170

A’s share = Rs. 150, B’s share = Rs. 280, C’s share = Rs. 170

(d) Jumbled Words

(i) TEANAIRM = TERMINAL

(ii) VAGNACEXETRA = EXTRAVAGANCE

(iii) VADIELTIONC = EDUCATIONAL

(iv) PKUNYBARTC = BANKRUPT

(v) TAESROSNC = ANCESTORS

Study Tips & Strategies

Effective Study Methods for General Science & Ability

Key Tips for Success

  • Create concept maps for scientific topics to visualize relationships
  • Practice mathematical problems regularly to improve speed and accuracy
  • Use mnemonics for remembering scientific terms and processes
  • Solve past papers to understand question patterns and time management
  • Focus on application rather than rote memorization

Important Formulas to Remember

Percentage Calculations:

Percentage = (Part/Whole) × 100
Percentage Increase/Decrease = [(New Value – Original Value)/Original Value] × 100

Algebra:

(a + b)² = a² + 2ab + b²
(a – b)² = a² – 2ab + b²
a² – b² = (a + b)(a – b)

Geometry:

Pythagoras Theorem: a² + b² = c²
Area of rectangle = length × width
Area of triangle = ½ × base × height