题目

Many people remember what _______ doing _____ October 15, 2003.        A．were they, on       B．they were, in        C．they were, on      D．were they, on 答案：C哺乳动物的运动是在哪种系统的调节下完成的A.运动系统B.呼吸系统C.神经系统D.循环系