A family of giraffes is living on the African savannah. The trees on the savannah are very tall and scattered. During the dry season, the giraffes must be able to reach the leaves of these trees for food.

A mother giraffe gives birth to two calves. Calf A has inherited a mutation that will make his neck longer than his mother when he is full grown. Calf B, on the other hand, has inherited a mutation that will make his neck shorter than his mother.
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From this story, which of the following statements can be inferred about genetic mutations?

Mutations cannot affect an individual because they can never be passed to the next generation.

B.
Mutations can be harmful at first, but the tall trees will cause Calf B's neck to grow longer than it would otherwise.

C.
Mutations may result in a favorable change that improves an organisms's ability to survive or an unfavorable change that harms an organism's ability to survive.

D.
Mutations are always harmful to an individual because they are changes in the DNA code.

Mutations are changes in the DNA code. Some mutations occur in body cells and only affect one individual; these mutations are not passed on to offspring. Some mutations occur in the DNA of sex cells and are passed from parent to offspring. The DNA in these sex cells determines what an organism will look like and what characteristics it will have.

Sometimes a mutation may result in a favorable change that, when passed on to the next generation, can improve an individual's ability to survive in its environment. At other times, a mutation may result in an unfavorable change that actually harms an individual's ability to survive. Because Calf A will have a longer neck than his mother, he should have no problem reaching the leaves of trees. On the other hand, a shorter neck may reduce Calf B's chance of obtaining enough food.

If the genes of sex cells contain mutations, they can be passed from one generation to the next. This means that when an organism with a mutation—either beneficial or harmful—lives to reproduce, the mutation can be copied and spread. Over time, the species as a whole may be affected.