题目

 (浙江省金华一中2008年5月高考模拟D篇) First it was jogging. Then aerobics（有氧运动）. Not too long ago, Americans discovered race walking. Now Americans are into a new fitness craze. They’re taking up bicycling. Over hills and down mountainsides and across quiet country roads, Americans are busily rolling along. The number of adults who ride for fitness is around 17 million, an increase of 70 percent over four years ago. Twice as many women as men are coming to the sport. Americans are falling in love with biking because it has speed, the benefits of jogging and17．“和谐号”列车从北京站缓缓驶出，加速行驶一段时间后又匀速行驶．因车站调度需要，该次列车路经西安站时停靠了一段时间之后，又开始加速、匀速行驶．下列图中可以近似刻画该列车在这段时间内速度变化情况的是（　　）A．B．C．D．