When he ________ the door，he found his keys were nowhere.
| A．would open | B．opened |
| C．had opened | D．was to open |
There were two roads ______ to the station.
| A．lead | B．led | C．leading | D．to lead |
The pilot asked all the passengers on board to remain ______ as the plane was making a landing.
| A．seat | B．seating | C．seated | D．to be seating |
The old man, ______ abroad for twenty years, is on the way back to his motherland.
| A．to work | B．worked | C．to have worked | D．having worked |
My cousin is old enough ______ himself.
| A．to wear | B．to put on | C．to dress | D．to have on |
He _____ have fallen asleep last night because he didn’t hear the phone call.
| A．may | B．should | C．can | D．must |