The more variation there is within genes, the better that organism's chances are for survival. This is because gene variations can cause an organism to develop new or different traits. Such variations come about either by sexual reproduction (and the mixing of two parents' genes) or by mutation. Mutations, remember, are rare and random changes in one of an organism's genes. Normally, there may be only one mutation in a thousand, or even a million, cell divisions. But with millions of cells in a complex organism or millions of similar one-celled organisms in a particular environment, such accidental changes are always possible. Since mutations are completely random, most mutated cells simply die. But sometimes a mutated cell survives and even benefits the organism. And if a mutation occurs in a sex cell, it can be passed on to the organism's offspring.

An organism with a mutated cell

A
most likely won’t pass its mutation down to offspring.

B
is more likely to survive than an organism without that mutation.

C
decreases the amount of genetic variation.

D
likely developed in order to help a species survive and grow.