一、句型转换：(40分)
1. He must help his parents. (变同义句) He ____ _____ help his parents.
2. She is busy because she must prepare for an English exam. (变同义句)
She is ______ _________because she must prepare for an English exam.
3. She takes care of her grandfather on the weekends. (变同义句)
She_____ _______ her grandfather on the weekends.
