题干
You shouldn't accept a lift from a person ________ you don't know him.
A：until
B：unless
C：if
D：whether
答案(点此获取答案解析）
C
You shouldn't accept a lift from a person ________ you don't know him.
A：until
B：unless
C：if
D：whether
，交流电流表A的示数是50mA则 （ ）
