某物体做直线运动,t=0时刻方向向东,其速度﹣时间图象如图所示,下列说法正确的是( )
A:第2s末,物体的加速度方向向东
B:第3s末,物体的合力为零
C:第3s末,物体离出发点最远
D:第4s末,物体正在向东运动
At the meeting, they discussed three difficult _______ to the study of mathematics.
根据句意及首字母提示完成单词(1)How many c____ are there in the world?(2)Can you write to me s____ ?(3)People in France do not like s____ English.(4)Koalas(树袋熊)come from A____ .(5)Miyoko l____ in Tokyo, Japan.
秦始皇统一后,规定以隶书作为标准文字,颁行天下。( )