The disappearance of dinosaurs is not necessarily caused by astronomical incidents. But _________explanations are hard to find.
| A． |
alternative |
B． |
aggressive |
C． |
ambiguous |
D． |
apparent |
____ on ten years of observation and study, the story shows that everyone dreams every night, whether they realize it or not.
| A．Basing | B．Based |
| C．Being based | D．Having based |
There are more than 740 million Chinese _______ to second-hand smoking in public places now.
| A．are being exposed | B．exposed |
| C．to expose | D．having been exposed |
What a pleasant birthday party! It is worthy_______all my life.
| A．being remembered | B．remembering |
| C．to remember | D．to be remembered |
“______ to Michelle and having two beautiful girls in my house never allows me to look down upon women,” said Obama.
| A．Marrying | B．Married |
| C．Having married | D．Being married |
The airport ______ next year will help promote tourism in this area.
| A．being completed | B．having been completed |
| C．completed | D．to be completed |