I _______ keep dogs for protection, but now I keep them as pets.

--Jack had prepared for the game for such a long time. We all thought he ________ it. -- What a pity! He ________ too nervous when playing it.

    --- Whose backpack is this?--- It        be Mary’s. She is looking for hers.

---Is Mr Hu in the reading room?---No, he _______be there. He has gone to Tianjin.

A good rest between classes ________ recover brain power to its best and make us perform better in class later.