A:took u
B:contributed to
C:carried out
D:made for
如图甲所示,一个单摆做小角度摆动,从某次摆球由左向右通过平衡位置时开始计时,相对平衡位置的位移x随时间t变化的图象如图乙所示.不计空气阻力,g取10m/s2.对于这个单摆的振动过程,下列说法中正确的是( )
When you see a fire,quickly go outside,never stop for toys or clothes.
have to show me climb mountains birthday cake play games far from make the bed traffic lights
美国著名人际关系学家戴尔•卡耐基说:“周围都有好朋友的人,比四面楚歌的人不知幸福多少。”这是因为( )