Nowadays there are still a number of students        school at various grades due to a lack of money in

some poorer areas. [ ]

A.  leaving out

B.  making out

C.  letting out

D.  dropping out

给老人欣赏音乐前，养老护理员应先调试音响设备，使音量（）。

A、适中

B、越小越好

C、越大越好

D、在150分贝以上