The smallest units that are considered to be alive are called

the cell is the smallest structural and functional unit of living organisms, which can exist on its own. therefore, it is sometimes called the building block of life. some organisms, such as bacteria or yeast, are unicellular—consisting only of a single cell—while others, for instance, mammalians, are multicellular.

answer; /// i do believe its (heredity); good luck

the answer to your question is:

c. complementary base-pairing