一辆汽车从车站以初速度为零匀加速直线开去，开出一段时间之后，司机发现一乘客未上车，便紧急刹车做匀减速运动。从启动到停止一共经历t=10 s，前进了15 m，在此过程中，汽车的最大速度为（   ）

    An English gent leman always takes an umbrella and wears a hat. Why? In England, it rains often. The rain comes at any time, so an umbrella is necessary (必要的) in people's life. English gentlemen love to take a long black umbrella. It is useful when the rain comes. And it is also a style. The hat plays an important part in their life too. If two men meet in the street,  they take off (脱掉)  their hats to show their respect (尊重) to each other. If a man visits his friend, he takes off his hat frst when he gets into the room. If he goes to a party, he can only put the hat on his chair, but not on the table. You don't have the two things, but you can still (仍然) be a gentleman. Always be nice to others and be ready to help others. Show your respect and love to old people, women and children. Never shout. Never lose your temper (发脾气).