－Where did you put the car keys?－Oh, I ______ I put them on the chair because the phone rang as I _______ in.

—You may find the key to the math problem on page 107．—Ah, it's so simple. I wonder why I _____ of that．

---You look very tired. ---Well, __________my lessons all the afternoon.

John is not a man to count on, and it is very likely that the work ____ by the time he arrives here.

Our plans for playing the football match today ________ by the terrible typhoon “Soulik”.