Environmental Science

Hydrogen is not a greenhouse gas because it does not absorb infrared radiation significantly. Methane, nitrous oxide, and ozone are all greenhouse gases that contribute to the greenhouse effect by trapping heat in the atmosphere.

Chlorofluorocarbons (CFCs) are the primary and most significant culprits responsible for damaging the ozone layer by releasing chlorine atoms that break down ozone molecules. While nitrous oxide also contributes to ozone depletion, CFCs have historically been the most impactful and widely recognized cause.

Lead is a well-known metal pollutant in urban air, primarily due to its historical use in gasoline and industrial emissions. The other metals listed are less commonly associated with air pollution in cities.

The primary cause of air pollution is the burning of fuels, especially fossil fuels like coal, oil, and natural gas, which release harmful pollutants into the atmosphere. Forests and fertilizers do not directly cause air pollution in the same way.

Deforestation leads to the removal of trees and vegetation that protect the soil. This causes an increase in soil erosion, landslides, and runoff because tree roots no longer hold the soil in place. Soil fertility decreases because the topsoil, which contains most nutrients, is washed away or degraded. Rainfall is not directly decreased by deforestation, although local microclimates may be affected. Therefore, the factor that decreases due to deforestation is soil fertility, making option D the correct answer.

Mercury is a heavy metal that accumulates in organisms and magnifies up the food chain, causing biomagnification in ecosystems. Lead, chromium, and copper do not biomagnify to the same extent as mercury.

The permissible noise level in residential areas during night time is generally set at 45 dB to minimize disturbance and protect residents' health and comfort. This standard is widely accepted in environmental noise regulations.

Eco-anxiety is the term used to describe a state of stress or worry caused by concerns about environmental issues and the future of the planet. It specifically relates to psychological distress linked to ecological problems.

The Southern Ocean, which surrounds Antarctica, is generally considered the least polluted ocean in the world due to its remote location and minimal direct human activity. It has far lower concentrations of plastic debris, chemical contaminants, and other pollutants compared to other oceans such as the Arctic, Indian, and South Pacific Oceans. While the Arctic Ocean is remote, it is increasingly affected by pollution due to climate change and human activities. Therefore, among the given options, 'None of the above' is the correct answer because the Southern Ocean is the least polluted, not the Arctic Ocean or the others listed.

The North Pacific Ocean is widely recognized as the most polluted ocean due to the Great Pacific Garbage Patch, a massive accumulation of plastic and other debris. This makes it the most polluted compared to the Indian and Arctic Oceans.