— Is John coming over this weekend?
— He should, but he _______ not. He seems to be busy these days.
| A．can | B．may | C．must | D．will |
Speak to him slowly _____ he may understand you better.
| A．since | B．so that | C．for | D．because |
You'll miss the train ______ you hurry up.
| A．unless | B．as | C．if | D．until |
When you read the book, you' d better make a mark _____ you have any questions.
| A．at which | B．at where | C．the place | D．where |
We'd better hurry ______ it is getting dark.
| A．and | B．but | C．as | D．unless |
I didn' t manage to do it _____ you had explained how.
| A．until | B．unless | C．when | D．before |