That virus has the power to all the valuable files people have stored in their computers.
| A．wash away | B．smooth away |
| C．put out | D．wipe out |
—John, how did your maths exam go?
—I thought I________， but in fact I came in the top ten in the class.
| A．should have failed |
| B．couldn't have failed |
| C．might have failed |
| D．mustn't have failed |
As you worked late yesterday, you________have come this morning.
| A．mayn't |
| B．can't |
| C．mustn't |
| D．needn't |
The weather turned out to be fine yesterday. I________the trouble to carry my umbrella with me.
| A．should have taken |
| B．could have taken |
| C．needn't have taken |
| D．mustn't have taken |
—She looks very happy. She________have passed the exam.
—I guess so. It's not difficult after all.
| A．should |
| B．could |
| C．must |
| D．might |
Don't be so anxious about that. Helen________a note.
| A．may leave |
| B．should leave |
| C．might have left |
| D．can have left |