题型:填空题 The mother looked _______ because her son hadn't been back. [ ]A. worry B. to worry C. worried 查看答案
题型:填空题 某分析天平的零点为“0”.在左盘上加重物w1,在右盘上加重物w2,天平的平衡点为+3分度.然后交换两盘的重物,则天平的平衡点变为-3分度,这说明:()A.w1=w2B.w1>w2C.天平的左臂比右臂长D.天平的右臂比左臂长安定E.天平的两臂相等 查看答案