If basic units of the plant body vary in size as well as shape, but all are very small, then what may vary in size as well as shape, but all are very small?

Answer choices:
- keeping food fresh for long periods of time
 - disease-causing microorganisms
 - A solid geometric shape
 - Unequal radiation absorption
 - Small countries.
 - Shapewear.
 - A water well.
 - Basic units of the plant body.

 

        Basic units of the plant body.  