阅读下面短文,从各小题所给的四个选项中,选出一个最佳答案。
People have different exercise habits. Some people exercise very often, while others seldom do it.
Mr. Smith is a very active person. He always goes to the gym after work. He exercises for about an hour every day. He usually does some weight — lifting and then runs on the treadmill. He says exercise makes him feel energetic and helps him sleep well at night.
Mrs. Green is a busy housewife. She doesn't have much time to exercise. She only exercises once or twice a week. She usually goes for a walk in the park near her home. She says walking is a simple but good way to keep fit.
Tom is a middle — school student. He often plays basketball with his classmates after school. He plays basketball about three times a week. He also likes swimming, but he only goes swimming in summer, so he swims hardly ever in winter.
Mary is a lazy girl. She never exercises. She says she is too busy with her studies and doesn't have the energy to exercise. But she knows she should exercise more to keep healthy.