读中国农业综合开发分布示意图,回答问题.
一排长椅共有90个座位,其中一些座位已经有人就座了.这时,又来了一个人要坐在这排长椅上,有趣的是,他无论坐在哪个座位上都与已经就座的某个人相邻.原来至少有____ 人已经就座.
读一读,判断句子正误。
Hello, I'm David. I'm ten. I'm fromShenzhen. I'm short and fat. I have a big head and a big body. I have two smalleyes and a big mouth. I have two long arms and two short legs. My feet aresmall. My hands are small too. What about you?
某质点的位移随时间的变化规律的关系是x=4t+2t2,x与t的单位分别为m和s,则质点的初速度与加速度分别为( )