The sun gets its energy through nuclear fusion. In this reaction hydrogen atoms fused to form helium atom. As a result huge energy is radiated on the surface of the sun. This reaction is repeated again and again resulting in the energy output continuously.
\(4 \mathrm{H}^{1} \rightarrow{ }_{2} \mathrm{He}^{4}+2+{ }_{1} e^{0}+\text { energy }\)

Floods, drought, soil erosion, loss of wild life and desertification will be caused by cutting down of trees.

High velocity of wind, air currents,flowing water, landslides, human activities.

(i) It burns without smoke and therefore causes less pollution.
(ii) An excellent way to get rid of organic wastes like bio-waste and sewage material.
(iii) Left over slurry is good manure rich in nitrogen and phosphorus.
(iv) It is safe and convenient to use.
(v) It can reduce the amount of green house gases emitted.

a) Forests are an important component of our environment.
b) Forest is dominated by
i) microorganisms
ii) flowering plants
iii) shrubs
iv) climbers
v) dense trees
vi) provide a vast habitat for wild animals.
a) Forests also contribute to the economic development of our country.
b) Forests are vital for human life.
c) It is a source for a wide range of renewable natural resource.
d) They provide wood, food, fodder, fibre and medicine.
e) Forest are major factor of environment concern like.
i) carbon sink
ii) regular climatic conditions
iii) increase rainfall
iv) reduce global warming
v) prevent natural hazards like food and landslides
vi) protect wildlife
vii) act as catchments for water conservation.
f) They also play a vital role in maintaining the ecological balance.

a) Both assertion and reason are true and reason is correct explanation of assertion.