People have lots of problems living in the central Australian desert, ____ the lack of water is the most serious one.
| A．of which | B．which | C．for which | D．where |
Kathy told me that all the doors and windows _______ when she arrived this morning.
| A．have cleaned | B．have been cleaned |
C．had cleaned | D．had been cleaned |
He devoted himself __________ to his research and got many achievements.
| A．entirely | B．extremely | C．carefully | D．certainly |
A great number of visitors ________ attracted to my hometown, and the number of foreigners there _______ quite large.
| A．are; are | B．are; is | C．is; are | D．is; is |
I ______ my winter holiday with my family in Beijing next month.
| A．am spending | B．spent | C．have spent | D．spend |
Ladies and gentlemen, please fasten your seat belts .The plane _____ .
| A．takes off | B．is taking off | C．has taken off | D．took off |