A:|2a|>|2a+b|
B:|2a|<|2a+b|
C:|2b|>|a+2b|
D:|2b|<|a+2b|
一只猴子抓在天花板上的细棒上,现使悬挂细棒的绳子断开,猴子和细棒一起向下运动,甲说此棒是静止的,乙说猴子是向下运动的,甲、乙两人所选的参考系分别是( )
用反证法证明命题:“三角形的内角至多有一个钝角”,正确的假设是( )
—Talking on WeChat .people's way of communicating in the recent few years.