RS232C逻辑0的电平为（）
A、大于+3V
B、小于-3V
C、大于+15V
D、小于-15V
参考答案：A
请将下列各电路元件符号正确连入电路图中．
Since you are free now, why not _____? [ ]
A. doing some washing
B. to do washing
C. to do some washing
D. do some washing
