Environmental Science

Nitrogen dioxide, sulfur dioxide, and carbon dioxide are all gases that contribute to air pollution in various ways. Therefore, none of the listed options are free from polluting the air, making 'none of these' the correct answer.

The yellow color in photochemical smog is primarily due to nitrogen dioxide (NO2), which is a reddish-brown gas that imparts a yellowish-brown hue to the smog. Other options like sulphur dioxide, carbon dioxide, and CFCs do not cause this characteristic color.

Burning oil and gas releases sulfur dioxide and nitrogen oxides into the atmosphere, which combine with water vapor to form acid rain. Acid rain damages forests and lakes by altering soil chemistry and harming aquatic life.

The Sundarbans Forest is the world's largest mangrove forest, spanning parts of India and Bangladesh. It is well-known for its extensive mangrove ecosystem, unlike the other options listed.

Pollutants introduced into the environment due to human activities are termed anthropogenic pollutants. This distinguishes them from natural pollutants that occur without human influence.

Acid deposition, commonly known as acid rain, causes damage to lakes and forests by lowering the pH of water bodies and soil, which harms aquatic life and vegetation. It does not lessen the greenhouse effect nor cause acid indigestion in humans.

The sum of all ecosystems on Earth is called the biosphere, which includes all living organisms and their physical environments. The other options refer to different layers or spheres of the Earth but do not represent the total of all ecosystems.

Salinization refers to the accumulation of soluble salts in soil, which can reduce soil fertility and affect plant growth. This process is commonly caused by irrigation practices and poor drainage.

Fine organic or inorganic particles suspended in air are called aerosols. These particles can be solid or liquid and remain suspended for a period of time, distinguishing them from gaseous pollutants.

Lead from motor car exhaust, especially in the past when leaded petrol was used, is known to cause neurological damage and mental diseases. The other options are either not primarily associated with mental disease or not common pollutants from car exhaust.