--- Why does the lake smell terrible?
--- Because large quantities of water _________.
| A．have polluted | B．is being polluted |
| C．has been polluted | D．have been polluted |
Three years ____ a long time for us students.
| A．are | B．be | C．is | D．have been |
To a doctor, the most important thing is _______.
A. to save b. saving C. to saving D. saved
Can you tell me ________?
| A．what are they doing that for | B．why they are doing for |
| C．why are they doing that | D．what they are doing that for |
I’d like to have a nice room ____.
A. live b. to live C. to live in d. live in
_____ Chinese people are ______ hardworking people.
| A．/,/ | B．a,/ | C．The, the | D．the,a |