题目

— Do you think I'm a good surfer?— Of course! I____ you earlier. You made it look so easy, graceful even. A . am watching B . was watching C . have watched D . had watched 答案：B已知全集U=R，集合M={x|x≥1}，则CUM为（ ）A．{x|x=1}B．{x|x≤1}C．{x|x＜1}D．{x|x＞1}