题目

Knowing how long the test would last, the students who finished ______ back and waited until the end of the exam.   A. settle    B. settled     C. settling    D. to settle 答案：B下列正确的有（　　） A、3x+3y=6xyB、7x-5x=2C、-（a-b）=-a+bD、-（a+b）=-a+b