图示两个相啮合的齿轮，A、B分别为齿轮O1、O2上的啮合点，则A、B两点的加速度关系是（）。
A.A
B.B
C.C
D.D
参考答案：B
（10成都1）世博“零碳馆”是中国第一座零碳排放的公共建筑。“零碳”中的“碳”主要指
A．CO
B．CO2
C．CH4
D．C
—What are you supposed to do while chatting with friends on the Internet so that the other person doesn't ?
—You are supposed to type quickly.[ ]
A. become annoying
B. feel boring
C. get bored
D. get used to it
