问题
If the machine makes a mistake — ____ rarely happens — it gives a warning in the form of a red light.
A:that
B:which
C:as
D:what
B:which
C:as
D:what
正确答案是：
同类题型
Do you know ______ this i-pad belongs to – Let me see. Oh, it’s ______.
If the work _____ by the end of this monthis delayed,the team will be fined.
词义替换。—What do you often do in your spare time—Play basketball.
______ will you comeback — In an hour.
They keys were __________ to our neighbours during our absence.