You are presented with the quiz "What happens as cells lose their ability to divide?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "aging occurs as cells lose their ability to divide" and "gerontology is the study of the aging process and old age". So, what's the best answer to the question?

Available options:
1). anemia
2). puberty
3). negative
4). radiation
5). getting old
6). replication
7). Dehydration
8). having a baby
The answer is:
5).