It remains __________ whether the medicine will work on the human body.
| A．seen |
| B．to seen |
| C．seeing |
| D．to be seen |
____ directly to the sun in summer will do great harm to our skin.
| A．Be exposed | B．Being exposed | C．Exposing | D．Exposed |
It rained heavily overnight and not until this morning____.
| A．did it stop | B．had it stopped | C．stopped | D．it stopped |
--Do you know what caused the accident? --- No, not yet. The matter _____.
| A．is being looked into | B．was being looked into | C．looked into | D．is looked into |
A new museum is being built in our city and it’ll be accessible to the citizens when___ next year.
| A．completing | B．is completed | C．to be completed | D．completed |
Robert failed to complete his education____ he found it hard to focus on his studies.
| A．although | B．if | C．because | D．while |