–May I go to the concert with you?

– I’m afraid not ______you have a ticket, because I have only one.

A. since        B. if        C. unless    D. though

--- My bike is broken. May I go ______ yours?     

---- Sorry, mine ________ broken down.

A. on, is           B. by, is               C. on, has      D. by, has

----May I go swimming this afternoon?
----I'm afraid not _______ you have finished your homework.

—May I go swimming this afternoon?
— I'm afraid not _______ you have finished your homework.

–Mom, may I go swimming with my friends in the river?

   –No, you _________. That’s too dangerous.

    A. won’t           B. don’t           C. needn’t        D. mustn’t