To maintain order within their cells and organs, all living things must
a. constantly change.
b. be able to move.
c. reproduce.
d. carry on metabolism.
e. extract energy from sunlight

The answer is d. carry on metabolism.

Metabolism includes all chemical reactions involved in maintaining order within cells and organs. The purpose of metabolism is a conversion of food or fuel to building blocks for macromolecules and to energy for cellular processes. It is involved in the elimination of waste, too. Regulation of metabolism is important for normal functioning of cells and organs.