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

The correct answer is: A. They emit light of a constant intensity.

Planets are much larger than stars and emit their own light. The light from a planet is not scattered by the Earth’s atmosphere in the same way as the light from a star, so planets do not twinkle.

Option B is incorrect because the distance of a planet from the Earth does change with time. Planets orbit the Sun, and the Earth orbits the Sun. This means that the distance between the Earth and a planet changes constantly.

Option C is incorrect because the intensity of light from a planet does not decrease with distance. The intensity of light from a star decreases with distance, but the intensity of light from a planet does not. This is because planets are much larger than stars and emit their own light.

Option D is incorrect because planets are not necessarily nearer to the Earth than stars. The distance between the Earth and a planet can be greater than the distance between the Earth and a star.