万用表的转换开关是实现（）。
A、各种测量种类及量程的开关
B、万用表电流接通的开关
C、接通被测物的测量开关
参考答案：A
The secretary worked late into the night, _______ a long speech for the international conference. [ ]
A. to prepare
B. prepared
C. preparing
D. was preparing
心脏右前斜位摄影，吞服钡剂的目的是为了观察
A．胃肠
B．气管
C．大血管
D．左心房
E．右心房
