–Have you ever traveled abroad?--Sure. I ____ the language of English in the USA two years after I graduated from the university.
My parents will not ______ my birthday party if I don't do well in my next test.
He ______ have sent the e-mail at an earlier time, but there was something wrong with the network.
—Can Professor Li be in the laboratory? —He ______ be; I saw him there half an hour ago.
My newly-purchased magazine is nowhere to be found. ______ I have left it on the train?
—Did your mother sleep well last night? —She ______ have slept through all those noises.