-Why does the water smell terrible?
-Because large quantities of water __________.
| A．is being polluted | B．have been polluted |
| C．is polluted | D．has been polluted |
They ______ on the program for almost one week before I joined them, and now we ____ on it as no good results have come out so far.
| A．had been working; are still working | B．had worked; were still working |
| C．have been working; have worked | D．have worked; are still working |
---What’s that terrible noise?
---The neighbors ____for a party.
| A．have prepared | B．are preparing | C．prepare | D．will prepare |
--- Hi ,Tracy, you look tired.
--- I am tired. I ____the living room all day.
| A．painted | B．had painted |
| C．have been painting | D．have painted |
---- Isn’t it hard to drive downtown to work?
---- Yes, that’s why I ____ to work by train.
| A．have been going | B．have gone | C．was going | D．will have gone |
---Why you are so worried?
--- I ___for my little son all the afternoon, I don’t know why he hasn’t come back so late.
| A．am waiting | B．have waited | C．have been waiting | D．waited |