正比例函数y=x的大致图象是（　　）

阅读理解

     Basketball is still a young game. It's over a hundred years old. In the winter of 1891, a certain college was having some trouble with its boy students. The weather was bad and the students had to stay indoors. As they couldn't play outdoors, they were unhappy, and some even got into fights from time to time.
　　Some of the teachers, at the college asked Dr. Naismith to invent a game so that the students might have something to play with. It was not easy to invent such a game because it had to be played indoors, and the court (球场) was not very large.
　　Dr. Naismith thought for a few days and invented a kind of ball game. It was a fast, wonderful game with much moving and passing of the ball. It was played between two teams. To make a score , the ball had to be thrown into the basket ten feet(英尺) above the floor on the wall . At each end of the court there was such a basket. At first, Dr. Naismith wanted to throw the ball into a box. As he could not find boxes of the right size, he had to use fruit baskets instead. That is how the game got its name.

B

    Running is becoming popular these days. Many of us run for our health. Doctors say many of the health problems come from these bad habits: eating too much, drinking too much, smoking, and not taking enough exercise. Doctors tell us, "Eat and drink less, don't smoke, and exercise more."

    Running is a good form of exercise because it helps build a strong heart. It also helps most people lose weight. One 68­year­old woman runs three times a week. She runs to lose weight.

    Running is good for health in other ways, too. Many runners say running keeps colds and other small health problems away." Running is my doctor, "says one man.

    Running can also help people to relax. So today men and women of all ages enjoy running.