–I wonder how much you charge for your service.
--The first two are free____ the third costs $30.
| A．before | B．as | C．when | D．while |
Are they still doing the experiment? They're supposed______it by the end of last class.
| A．finish | B．finished | C．to finish | D．to have finished |
－Hi, I didn't know you had come back! Have you finished your teaching in America?
－Yes. I______Chinese there for more than two years.
| A．have been teaching | B．was teaching | C．taught | D．had taught |
Better be more careful______you've made a mistake.
| A．when | B．where | C．and | D．that |
－What about______party you went to yesterday evening?
－Oh, it was boring, you know, party like that!
| A．the; a | B．a; the | C．the; / | D．the; the |
25．A heavy drought is hitting the south－west part of China, ______severe problems for hundreds and thousands of people and cattle to get fresh drinking water.
| A．causing | B．caused | C．to cause | D．having caused |