—Have you known Dr. Jackson for a long time?—Yes, since she _________ the Chinese Society.

This is John’s photo. We miss him very much. He _______ trying to save a girl in the earthquake.

---What were you doing when Tom came to see you?---I had just put on my overcoat and_____ to visit my friends.

---Those shoes won't_____for mountain-climbing.　　---_____this pair be OK?

—Look! Somebody ______the blackboard．—Well, it wasn't me．I didn't do it．