— Do you often go swimming_____ Sunday mornings?

— Yes. Why not _____with me this Sunday?

A．on, go

B．in; to go

C．on; going

D．in going

一个物体做匀速直线运动，它在第10s的速度是10m/s，则它在前4秒内的速度是______，按此速度运动10min，这个物体通过的路程是______km，若通过200m的路程需要______s．