Why do we grow old? This is a question that people have asked since the beginning of history. Now biologists are looking for scientific answers to this question. They think that aging is part of our genetic program. From the evolutionary point of view this makes sense. A person who can no longer have children is not useful to the species, so he or she
a. grows old and dies.
b. lives a long life.
c. stops having children.
d. has a genetic program.