下列说法中正确的是[ ]

A. 匀速圆周运动是一种匀速运动

B. 匀速圆周运动是一种匀变速运动

C. 匀速圆周运动是一种变加速运动

D. 物体做圆周运动时其向心力垂直于速度方向，不改变线速度的大小

根据中文提示写出单词或词组，使句意完整、正确。

小题1:—In the past, parents couldn’t afford an education for their children.

—Yes. But now great changes have taken place in China.

—The government will            （提供）poor people with nice houses.

—Sounds wonderful.

小题2:We believe we’ll            （成功）in finishing the hard work.

小题3:          （垃圾）pollution influences our environment.

小题4:Edison made many great            （发明）in his life.

小题5:He couldn’t find a            （合适的）place to take photos.