Students can easily fall behind in their studies ____ they don’t manage their spare time carefully.
| A．though | B．if | C．since | D．until |
The witnesses________by the police just now gave very different descriptions of the fight.
| A．questioned | B．being questioned |
| C．to be questioned | D．having questioned |
The airport________next year will help promote tourism in this area.
| A．being completed | B．to be completed |
| C．completed | D．having been completed |
You cannot accept an opinion________to you unless it is based on facts.
| A．offering | B．to offer |
| C．having offered | D．offered |
Laura was away in Paris for over a week.When she got home，there was a pile of mail ________for her.
| A．waited | B．to wait |
| C．waiting | D．was waiting |
The room is empty except for a bookshelf ________ in one corner.
| A．standing | B．to stand |
| C．stands | D．stood |