Given the task definition and input, reply with output. In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

Article: American actress Marisa Tomei won an Academy Award for her work in the 1992 movie My Cousin Vinny. People laughed when they saw her film character telling a boyfriend that they need to get married. Why marriage? Because her biological clock is ticking and she wants a baby. "Well I hate to bring it up because I know you got enough pressure on you already. But...we agreed to get married as soon as you won your first case(law case). Meanwhile, ten years later...my niece...the daughter of my sister is getting married. My biological clock is ticking like this (stomp, stomp, stomp). And the way this case is going...I ain't never getting married." "Lisa, I don't need this. I swear to God I don't need this right now." Using it this way, a biological clock means the time in a woman's life when she is able to bear children. In the not-so-distant past, most people thought that when a woman reached her 40s it was too late for her to have children. The time on her biological clock had run out. Well, that has changed. These days some women are resetting their biological clocks. They are giving themselves more time to have children. Make no mistake. Being a "Single Mother by Choice" is very different from younger women who find themselves pregnant, perhaps not by choice. Generally speaking, single mothers by choice are older and well educated. They are usually financially secure and successful in their careers. So, they have the money. What they may not have is a partner. This is the place in life where writer Kerry Reichs found herself several years ago. She says she did not plan to become a single mother. She says she just did not find the right partner. "Well, I think I had a set of standards for the partner I was looking for and I didn't meet anyone that fit those standards. And, at 39 I found myself single, without children and I wanted them very much. So, I made the difficult decision that I could do this on my own.
Answer: It refers to a women's certain life period.
According to the passage, what is a biological clock?