Cells vary in size as well as shape, but all cells are very small, and bacteria are single-cell microorganisms that are so small they can only be seen with a microscope. Given these facts, cells vary in size and shape and can only be seen with what among the following options:
- a microscope
 - heightened senses
 - a telescope lens
 - colors
 - Solar energy
 - by indirect light
 - a good eye
 - A computer


 

 a microscope        