He made another wonderful discovery, ______ of great importance to science.
| A．which I think is | B．which I think it is |
| C．which I think | D．I think which is |
— Could I have a word with you, mum? — Oh, dear, if you ______.
| A．can | B．may | C．must | D．should |
The reason ______ at the meeting for being late was not reasonable.
| A．why he gave | B．what he gave | C．he gave | D．on which he gave |
With the guide _______ the way, we finally got to the village which we were looking for.
| A．led | B．leading | C．to lead | D．had led |
To qualify yourself for this kind of new job, I recommend that you ________ some online courses.
| A．to take | B．taking | C．take | D．would take |
— I hear it will rain tomorrow.
— It _______ true. You see, there are so many black clouds in the sky now.
| A．won’t be | B．will be | C．may be | D．may not be |