A:①②
B:①③
C:②④
D:②③
一个质点运动的v﹣t图象如图所示,则相对应的s﹣t图线正确的是( )
“李宗仁指挥中国军队歼敌一万多人,取得抗战以来的重大胜利。”请判断这是什么战役( )
Mr. Chen is very _________ every day. He has no time to help his daughter with her homework.