How has the study of mitosis affected scientists’ knowledge of cancer?
it led to a study of how to induce cancer cells to divide more rapidly.
it led to an understanding of how cancer cells divide so rapidly.
it led to the development of contact-inhibition regulators.
it led to the discovery of how to prevent cancer cells from dividing.

The question is asking how has the study of mitosis affected scientists’ knowledge of cancer. Mitosis is a type of cell division ( so we reject answer c, since it doesn't have to do with cell division) and what we want is to have the cells divide slower (so we reject answer a), but unfortunately, we don't know how to do it yet (so we reject answer d) - the correct answer is: It led to an understanding of how cancer cells divide so rapidly.

The answer is magnitude measures the effects of an earthquake on the area , while the intensity measures the strength of an earthquake.