Question

which is the smallest unit of all living things?
a cell
b virus
c bacterium
d brain

Explanation:

Cells are the basic structural and functional units of all living organisms. Viruses are not considered living in the strict sense as they cannot reproduce without a host cell. Bacteria are single - celled organisms but are larger than cells in the context of being a more complex unit. The brain is an organ made up of many cells.

Answer:

A. cell