学会自主学习,要求我们每一个人[ ]
①独立自主完成作业
②从不向别人寻求帮助
③逐渐摆脱对父母的依赖
④学会严格自律,加强自我管理
A、①②③
B、②③④
C、①②④
D、①③④
答案:D
设a、b满足a2+b2-2a=0,则2a-b的最大值为______.
—Hi, Susan, you look tired.
—I ______ for months for the coming celebration for the school’s 60th anniversary.
A.was preparing
B.have been preparing
C.had prepared
D.prepare