—Why can your teacher know so much about London?

—He ________ have been there before．

A． may         B． must         C． ought to         D． should

No doubt bad seeds ________ produce bad corn.

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28．— Is Mike going there by bus?    

— He ought to, but he ________ not. He likes riding his bike.

—Why does Sara know so much about Angkor Wat?

—She ______ have been there, or…

A．must                  B．ought to                    C．can                    D．may

一Where are you going for your holidays?    

―I haven’t decided yet. I      go to England．   

    A．can          B．may             C．must          D．ought to