Physics
Green house effect is the heating up of the Earth's atmosphere which is due to

The infra-red rays
G-rays
The ultraviolet rays
X-rays

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Physics
Planets do not twinkle because

They are nearer to earth and hence we receive a greater amount of light.
Their distance from the earth does not change with time
They are very far away from the earth resulting in decrease in intensity of light
They emit light of a constant intensity

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