Not until the press reported the pollution _________ why the water supply had been cut off.
| A．people did know | B．people had known |
| C．did people know | D．had people known |
If you want to see a doctor, fix the date with him ahead of time. This is a common ___________ in the USA.
A. habitB. lawC. ruleD. custom
He___________ when the bus came to a sudden stop.
| A．was almost hurt | B．was to hurt himself |
| C．was hurt himself | D．was hurting himself |
—What would you wish to do if you were a college student again?
—That's very hard to say, but I wish I___________ when I was a college student.
| A．has not studied biology | B．did study biology |
| C．had studied biology | D．studied biology |
His parents meant him_____________ scientific research, but he showed no interest and turned poet.
| A．going in for | B．to have gone in for |
| C．to go in for | D．having gone in for |
—Why didn't you answer my phone when I phoned you at about 11 p. m. yesterday?
—I ___________and failed to hear the phone.
| A．might have slept | B．must be sleeping |
| C．might be sleeping | D．must have been sleeping |