Question

which is a part of the cell theory? cells come from pre-existing cells cells have a nucleus organisms with one cell must be seen with a microscope organisms must have more than one cell to live

Explanation:

The cell theory has three main parts: all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells come from pre - existing cells.

• Option "cells have a nucleus" is incorrect because prokaryotic cells do not have a nucleus, and the presence of a nucleus is not part of the cell theory.
• Option "organisms with one cell must be seen with a microscope" is incorrect as the requirement of being seen with a microscope is not part of the cell theory; it is just a characteristic of most unicellular organisms due to their size.
• Option "organisms must have more than one cell to live" is incorrect because unicellular organisms (organisms with one cell) can live and function properly.
• Option "cells come from pre - existing cells" is one of the key tenets of the cell theory.

Answer:

A. cells come from pre - existing cells