Fact 1: Cells vary in size as well as shape, but all cells are very small.

Fact 2: Bacteria are single-cell microorganisms that are so small they can only be seen with a microscope.

Given the two facts above, answer the question "Cells vary in size and shape and can only be seen with what?" with the following options: 
- a microscope
 - heightened senses
 - a telescope lens
 - colors
 - Solar energy
 - by indirect light
 - a good eye
 - A computer


 

 a microscope        