He cut off the electricity immediately he found the dangerous situation, thus ____ a fire accident.
| A．prevented | B．to prevent | C．would prevent | D．preventing |
31．—Can you tell me what time the flight to Detroit leaves?
—I'm sorry, but it ______．
| A．has been canceled | B．had been canceled |
| C．has canceled | D．had canceled |
30．Napoleon would have taken over the world if he ______ the Battle of Waterloo．
| A．wins | B．won | C．had won | D．has won |
29．—How did he break his head while swimming?
—______ my warnings, he dived straight into the shallow water．
| A．To ignore | B．Ignored | C．Ignoring | D．Being ignored |
28．You ______ very fast if you went from New York to Boston in six hours．
| A．should drive | B．would have driven |
| C．may drive | D．must have driven |
27．—Do you know when Phil's coming?
—He ______ 4: 00．
| A．says | B．has said | C．had said | D．Said |