Not until he failed in the last examination _________ he should have spent more time on study.
| A．did he realize | B．he realized | C．did he not realize | D．he didn’t realize |
___ is left over may be put into the refrigerator, ____ it will keep for two or three weeks.
| A．Whoever; when | B．Whenever; which |
| C．Whatever; where | D．Whichever; while |
Modern science has given clear evidence ____ smoking can lead to many diseases.
| A．what | B．which | C．that | D．where |
Three young men have been arrested because they were caught ___ an old lady last night.
| A．robbed | B．to rob | C．rob | D．robbing |
______ a little earlier, you could have got a copy of his latest book.
| A．If you would arrive | B．If you arrived |
| C．Should you arrive | D．Had you arrived |
Don't be afraid to ____ help if you have any further problems.
| A．beg | B．hesitate | C．desire | D．seek |