It is hard to say what kind of person he is. Sometimes he is very friendly; at other times he ___ be very cold.
According to Lee, it was Ben’s carelessness that _______ the accident. But Ben _______ his wrong doing.
I believe that those mountains ________ with trees in a few years’ time.
______ the scene, he couldn’t help thinking of the description in a book ____ by a British novelist.
________ many changes have _______, we should keep pace with the changes too.
He said it was this classroom _______ he found his lost watch and _____ he would take good care of it from then on.