Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 44 to 50.

A diver descends into an underwater cave, a scientist researches a dangerous disease, and an entrepreneur invests in a new business. Each time we try something new, we take a risk. Sometimes, like the diver or the businessman, we take big risks, usually for obvious reasons-for fame, for money, or to save lives. Most people will take some risk to achieve one of these goals. But as the danger increases, the number of people willing to go forward decreases. Only extreme risk-takers continue on. The question is: What exactly drives these people to go on when others would stop?

To answer this question, scientists are studying the biological factors involved in risk-taking. Their research focuses on certain chemicals in the brain. An important chemical in risk-taking is dopamine. It motivates us to seek out and learn new things, and it helps us process emotions like anxiety and

fear. When we accomplish a task, dopamine produces a feeling of satisfaction; it makes us feel good. The riskier the task, the more dopamine we produce, and the better we feel.

Dopamine production may make us feel good, but being in a high-risk situation for an extended period of time is also stressful and can be dangerous. Successful risk-takers must learn to deal with the fear associated with high-risk situations to reduce stress and stay safe. In reality, adapting to risk is something we all learn to do. Take, for example, learning to drive a car. At first, a new driver may be afraid to travel on freeways. In time, though, as the driver gains experience, he or she will move comfortably into speeding traffic and will worry less about the danger. The work that marine biologist and deep-sea diver Rhian Waller does illustrates this well. She studies life in some of the deepest and coldest waters on Earth. How does Waller control her fear and stay safe in these high-risk situations?

Of course, a person doesn't have to be a deep-sea diver to be a risk-taker. Taking risks is part of being human. We are all motivated to experience new things. In order to do so, we have to take chances and, of course, we may fail. "It comes with practice," she says. "It's knowing exactly what to do when something goes wrong. We prepare well for each of our expeditions, and we try to minimize the number of risks we take."

(Adapted from Reading Explorer by Nancy Douglas and David Bohlke)

The word it in paragraph 2 refers to _______.