Free Environment and Atmosphere MCQs with Answers

41. The salinity of sea water is determined by the amount of common salt (Sodium Chloride) in __________ of sea water.

• A. 1 gram
• B. 10 grams
• C. 1 kg
• D. 10 kg

Explanation: Sea-water salinity is conventionally expressed as the mass of dissolved salts in one kilogram of seawater, commonly about 35 grams per kilogram. Strictly, salinity includes all dissolved salts, not only sodium chloride.

42. At night, Plants intake __________ and release __________?

• A. Oxygen - Carbon dioxide
• B. Carbon dioxide - Oxygen
• C. Oxygen - Carbon monoxide
• D. None of theseCarbon monoxide - Oxygen

Explanation: In darkness, photosynthesis stops but respiration continues, so plants generally take in oxygen and release carbon dioxide. During daylight, photosynthesis usually reverses the net gas exchange.

43. The most abundant element in the Earth's crust is __________?

• A. Oxygen
• B. Hydrogen
• C. Carbon Dioxide
• D. Silicon

Explanation: Oxygen is the most abundant element in Earth's crust by mass, largely because it is combined with silicon and metals in widespread rocks and minerals. Silicon is second by mass, not first.

44. Which One of the Following Is Not a Greenhouse Gas?

• A. Methane
• B. Hydrogen
• C. Nitrous oxide
• D. Ozone

Explanation: Hydrogen is not normally classified as a greenhouse gas because it does not significantly absorb outgoing infrared radiation. Methane, nitrous oxide and ozone all contribute to the greenhouse effect.

45. which type of rock is made from molten(Fire) material within the earth surface?

• A. Sedimentary rock
• B. Schist rock
• C. Igneous rock
• D. Metamorphic rock

Explanation: Igneous rocks form when molten magma or lava cools and solidifies. Sedimentary rocks form from deposited material, while metamorphic rocks are altered by heat and pressure without melting.

46. As one moves away from the surface of earth with higher altitude ,the atmospheric pressure will go on ________.

• A. Increasing
• B. Decreasing
• C. Remains same
• D. First decreases then increases

Explanation: Atmospheric pressure decreases with altitude because there is less air above exerting weight on a given area. This is why breathing becomes more difficult at very high elevations.

47. Burning of Fossil Fuels Results In ____________?

• A. Increased oxygen level
• B. Decreases greenhouse gases
• C. Increased greenhouse gases
• D. Increased ethane level

Explanation: Burning coal, oil and gas releases carbon dioxide and other gases that increase the atmospheric greenhouse effect. It does not increase oxygen, and the relevant rise is mainly in carbon dioxide rather than ethane.

48. The height at which atmospheric pressure declines by a factor of e (an irrational number equal to 2.71828) is called __________.

• A. Average height (H)
• B. Scale height (H)
• C. Mean height (H)
• D. Standard height (H)

Explanation: The scale height is the vertical distance over which atmospheric pressure falls to 1/e, or about 36.8%, of its original value. It depends on temperature, gravity and the mean molecular mass of the air.

49. Exosphere interacts with ___________ of Earth at roughly distance of 10,000 km.

• A. Electrosphere
• B. Magnetosphere
• C. Spectrosphere
• D. Echosphere

Explanation: The outer exosphere merges gradually with space and interacts with Earth's magnetosphere, the region controlled by the planet's magnetic field. The other listed “spheres” are not recognised atmospheric regions.

50. __________ contains the ozone layer.

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Ionosphere

Explanation: The stratosphere contains the concentrated ozone layer, generally about 15–35 km above Earth's surface. Ozone there absorbs ultraviolet radiation and causes temperature to increase with altitude.