Stefan ________ from heart attack for more than ten years, but now he’s healthy and energetic.
| A．had suffered | B．suffered |
| C．has suffered | D．has been suffering |
He paid for a seat, when he________have entered free.
| A．could |
| B．would |
| C．must |
| D．need |
________such heavy pollution already, it may now be too late to clean up the river.
| A．Having suffered |
| B．Suffering |
| C．To suffer |
| D．Suffered |
John, look at the time，________you play the piano at such a late hour?
| A．Must |
| B．Can |
| C．May |
| D．Need |
—Are you coming to Jeff's party?
—I'm not sure. I________go to the concert instead.
| A．must |
| B．would |
| C．should |
| D．might |
Mr. Bush is on time for everything. How________it be that he was late for the opening ceremony?
| A．can |
| B．should |
| C．may |
| D．must |