When the news came _______ the war broke out, he decided to serve in the army.

A．since

B．which

C．that

D．because

一物体做匀减速直线运动，初速度为10m/s，加速度大小为1m/s²物体在停止运动前ls内的平均速度为（）

A.5.5m/s

B.5m/s

C.1m/s 

D.5m/s