某同学在百米比赛中,以6.0m/s的速度迅速从起点冲出,到50m处的速度是8.2m/s,在他跑的全程的中间时刻即t1=6.25s时的速度为8.3m/s,最后以8.4m/s的速度冲过终点,他在百米比赛中平均速度的大小为____ m/s.
① How much cheese do you want ? ____ A. They will come tomorrow.
② How many things are there ? ____ B. I'm shopping .
③ When will these things come ? ____ C. Half a kilo.
④What are you doing ? ____ D. Thirty-seven.