Natural Resources (Class-IX)

This is the correct answer as all these pollute the air. H₂S or hydrogen sulphide is a very poisonous, corrosive, flammable, and explosive gas. Carbon monoxide is a deadly, colourless, odourless and poisonous gas. It is produced by the incomplete burning of various fuels. Cement and asbestos also produce gases that pollute the air.

This statement is correct. Green plants convert carbondioxide into glucose in the presence of sunlight. The process is called photosynthesis and carbon dioxide is fixed by plants through this. Thus, this is the correct answer.

This is the correct answer as lichens are found to be very sensitive to the levels of contaminants like sulphur dioxide in the air. In places where no lichens are growing, it is often a sign that the air is heavily polluted with sulphur dioxide.

This is the correct answer choice as this statement is incorrect. Sand and water do not heat up at the same rate. Sand heats up faster than water as the specific heat of sand is lower than the specific heat of water.

This is the correct answer as mustard is not leguminous.

This is the correct answer as both pesticides and fertilizers cause water pollution.

This is the correct answer as both statements are correct. Most of the water on Earth’s surface is found in seas and oceans and is saline. All cellular processes take place in a water medium.

This is the correct answer as deforestation and overgrazing cause the denudement of top soil and thus, cause soil erosion.

This is the correct answer as nucleic acids such as DNA and RNA and proteins are biologically important compounds that contain both oxygen and nitrogen.

This is the correct answer as the first ever hole in ozone layer was first observed over Antarctica.

This is the correct answer as both statements are correct. Flow of energy in biosphere is unidirectional from non-living to living things. Amount of minerals cycling through living and non-living components remains constant.

This is the correct answer as argon is a noble gas which does not form oxides. It is not a greenhouse gas.

This is the correct answer as these statements are correct. Lichens grow on the surface of rocks and while growing, they release certain substances that cause the rock surface to powder down and form a thin layer of soil. Mosses grow on this surface and they cause the rock to break up further. Bits of decayed living organisms in the soil are called humus.

This is the correct answer. Blue-green algae, apart from rhizobium bacteria, can fix free nitrogen.

This is the correct answer. Nitrosomonas are nitrifying bacteria and their role is to change ammonia into nitrites. They conduct ammonification. Nitrobacter change nitrites into nitrates. They conduct nitrification. Pseudomonas are denitrifying bacteria and change nitrates into free nitrogen.