题目

物体以速度v匀速通过直线上的A、B两点，所用时间为t，现在物体从A点由静止出发，先做匀加速直线运动(加速度为a1)到某一最大速度vm，然后立即做匀减速直线运动(加速度大小为a2)至B点速度恰好减为0，所用时间仍为t.则物体的              ( )． A．vm只能为2v，与a1、a2的大小无关 B．vm可为许多值，与a1、a2的大小有关 C．a1、a2必须是一定的 D．a1、a2必须满足＝speak，class，take，exciting，by，ability，other，great，one，because  Only when you want to do something, can you do it well. Eight years ago,I was 1 into the English world. It was fresh to me then. I feel lucky 2 I met with a good teacher. Her teaching style was special and we were active and 3 in classes. So when I 4 got touch with English, it interested me a lot.  As is known to all，writing，reading， listening and5are the basic skills of English. They should be well coordinated(使协调).But many students pay less attention to speaking. At school, on every weekend, I go to the English corner to chat with 6in English. It doesn't need much vocabulary (词汇)but fluency(流利).My spoken English is improved 7 doing this. And this vacation I plan to have oral 8 in Beijing. I think the more you speak，the 9 progress you will make.In all, there are many ways to learn English well. We must make great efforts and develop all kinds of 10 ―. Never give up, and we'll succeed one day.1._______  2._______  3.__________ 4.__________ 5._______  6.__________ 7.__________ 8._______  9.__________ 10._______