---Must I be back home before 6 o’clock? ---No, you ____. But don’t be too late.

--Whose backpack is this? ---It            be Jim’s. Look, his student’s card is in it.

(2013·安徽高考)It ________ be the vocabulary that caused you the problem in the exercise because you know a lot of words.

You _______ write the poem down. Our teacher will give us a copy. 

– Amazing! You _____ have won the first prize in the national English speech contest!– I’m lucky that all my efforts have finally paid off.