Mary decided not to work on the program at home because she didn’t want her parents to know what she __________.

A．has done

B．had done

C．was doing

D．is doing

用于系统设备搜索与跟踪能力试验的微（电）波暗室一般是什么体型（）。

A.矩形

B.圆形

C.异性

D.多边柱形