Answer:
C) a living single-celled organism such as phytoplankton
Chromosomes must be copied before cell division so an equal number can go into each new cells.
It is important because that way you can group certain things, such as colors, size, shapes, etc.
Prokaryotic cells also have loose/free/a ring of DNA (not confined to a nucleus) and they can also sometimes have a capsule (slimy outer layer). Also they have slightly smaller ribosomes- 70s instead of 80s.