Which two of the following are MAIN ideas of the article? 1. Carbon shifts from one area to others through the slow and fast carbon cycles. 2. When the ocean takes in more carbon than it releases, it becomes more acidic. 3. Rain breaks down rocks, which are eventually brought to the ocean. 4. Human behavior has led to increased carbon levels in the atmosphere.

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.

"a.) well–developed vascular system."

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