Mention one way by which oxygen is released into the atmosphere.

The endoskeletons and exoskeletons of various animals are also formed from:

Write the names of two biologically important compounds that contain both nitrogen and oxygen.

State reasons for the following:
$(i)$ Excess burning of coal causes greenhouse effect.
$(ii)$ Soil is a mixture.
$(iii)$ Temperature ranges from $-190^{\circ} C$ to $110^{\circ} C$ on the surface of the moon.

One of the following processes is not a step involved in the water cycle operating in nature:

$(i)$ An increase in temperature of the water bodies would lead to water pollution: Explain.
$(ii)$ Suggest any two methods to prevent water pollution.