单选题：—I regret to say that I failed to rank first in the terminal..

_____ they decide which college to go to, students should research the admission procedures.A. As B. WhileC. UntilD. Once

The boy _____ to his mother that the hen _____ on the ground _____ two eggs.A. lay; lying; layB. lay; lay; laid C. lied; lying; laid D. laid; lay; laid

He decided that he wouldn't attend her birthday party ____ he was invited to.A. becauseB. as if C. as though D. even if

—Did Ann fail in English?—She ________. Don't you notice that she looks depressed?A．mightB．mustC．may haveD．could have

_____ I had seen him yesterday at the airport!A. If B. If only C. Only if D. Since