Protein compound which brings about changes in other organic compounds without being changed or broken down itself

Enzymes

Enzymes are biological substances that catalyse chemical reactions and they regulate the rate at which chemical reactions peoceed without itself being altered in the process. However, enzymes act on the molecules called substrate and thereby convert them different molecules known as products.

sadness is not good

explanation:

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.