A:减小压强
B:缩小体积
C:降低温度
D:增大氢气的浓度
下列关于合力的叙述中正确的是( )
—________ is that man?
— You don't know him? He is Ma Yun.
如图,平行四边形ABCD的周长为16cm,AC,BD相交于点O,EO⊥BD交AD于点E,则△ABE的周长为( )