20. I got up early this morning, but I ________ so because I was not on duty today.
| A．mustn’t have done | B．needn’t have done |
| C．didn’t need to do | D．can’t have done |
The biggest whale is ________ blue whale，which grows to be about 29 meters long—the height of ________ 9story building.
| A．the；the | B．a；a | C．a；the | D．the；a |
We can never expect ________ bluer sky unless we create ________ less polluted world.
| A．a；a | B．a；the | C．the；a | D．the；the |
What ________ pity that you couldn't be there to receive ________ prize!
| A．a；a | B．the；a | C．a；the | D．the；the |
Now that we've discussed our problem，are people happy with the decisions ________？
| A．taking | B．take | C．taken | D．to take |
The children all turned ________ the famous actress as she entered the classroom.
| A．looked at | B．to look at |
| C．to looking at | D．look at |