Coal is the most polluting as it releases the maximum amount of solid particulates into the air and also leaves behind a residue after burning.

Solar cell is the device which is used to convert solar energy to electricity.

The maximum temperature that a solar cooker can attain is 100° - 140°C. At this temperature, food can be cooked.

Charcoal is left behind; water and volatile material get removed.

The slurry left behind in a biogas plant contains nitrogen. 

If the temperature difference between water at the surface and water at a depth of up to 2 km is 20 K, then these plants work.

Unequal heating of landmass and water bodies by solar radiation generates air movement and causes winds to blow. Difference in temperature in the polar and equatorial regions also causes very strong polar winds to blow.

Large tracts of land get submerged under water and the vegetation, which is submerged, gives rise to methane gas; both are the negative impacts of reservoir-type hydropower plants. 

Carbon monoxide is not a greenhouse gas.

Uranium is used in fission process. It causes serious health problems. It causes environmental pollution.

During the process or reaction, a nuclear power plant gives the substance which pollutes the environment. Hence, option (2) is correct.

A glass sheet, a mirror and a black box are required to make a solar cooker.

A hydropower plant helps in irrigation and in controlling floods.

Hydrogen bomb is based on nuclear fusion reaction and nuclear bomb is based on nuclear fission reaction.

High calorific value and ease of transport are the characteristics of a good fuel.