When and where this took place_________still unknown.
| A．are | B．were | C．is | D．has |
The beautiful town, _____ we spent our summer vacation last year , lies at the foot of a mountain．
| A．whose | B．which | C．where | D．why |
—It’s such a beautiful day． Why not have a picnic with us?
—_____． But I have a lot of homework to do．
| A．Don’t mention it | B．It’s up to you |
| C．I have no time | D．I’d love to |
—Listen! There is a knock on the door． Who _____ it be?
—It must be Jack． Just now I sent for him．
| A．shall | B．can | C．must | D．might |
—What made her so happy?
—_____ her son passed the driving test．
| A．That | B．Because | C．Since | D．When |
I would have come earlier, but I _____ that you were waiting for me．
| A．didn’t know | B．hadn’t known |
| C．haven’t known | D．wouldn’t have known |