Karen is looking at a slide of an onion root tip under a microscope. She noticed that not all the cells look the same. Which of these best describes why all the cells are not identical?

A). The root is continuing to grow so the cells are going through mitosis
B). Some of the cells are cells and others are cells in the stem
C). There is a problem with the slide and it must be contaminated
D). The cells are turning into the actual