用所给词的适当形式填空 1. —What ______ (happen) to Jim last night? —He fell down and hurt his leg. 2. By the time he got to school, classes______ already ______ ( start). 3. I ______( work) out five math problems by the time the teacher came in. 4. When I got up this morning, my brother ______( got) into the bathroom. 5. By the end of last term, we ______(learn)many English words.