You can come here to ask me ________ if you have any questions.
| A．at one time | B．at a time | C．at any time | D．all the time |
The most impressive sight in China，one of the wonders of the world，_____ the Great Wall.
| A．is | B．are | C．was | D．were |
The factory used 65 percent of the raw materials,the rest of whichsaved for other purposes.
| A．is | B．are | C．was | D．were |
—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 |
One-third of the country____covered with trees and the majority of the citizens_______black people.
A is；are B is；is C.are；are D.are；is
Was it not until you began to work —— how much time you had wasted?
| A．did you realize | B．that you realized | C．did you not realize | D．that you didn’t realize |