The mesosphere burns up most meteors and asteroids before they are able to reach the earth's surface.The mesosphere is the coldest atmospheric layer surrounding the earth. It becomes cold enough to freeze water vapor in its atmosphere into ice clouds.
The Salt Strike was the most aggressive revolt of the Indian National Congress. The correct option among all the options that are given in the question is the first option. This was actually a civil disobedience movement in a non violent matter. This is also an important movement in the history of India.
The ozone layer is comprised of ozone, an atom which is constructed of 3 oxygen molecules.
Hope that helped =)