Which statement is true of crossing over?

A. It occurs during prophase of mitosis.

B. It allows for genetic variation.

C. It occurs only in animals.

D. It stops genetic variation.

B. It allows for genetic variation.

Explanation:

As prophase progresses, homologous chromosomes come to lie side by side and become intertwined rather like a zipper. This process is called synapsis. During synapsis, homologous chromosomes exchange genetic material between one another which allows for genetic variation. This exchange is called crossing over.