1914年7月，德皇威廉二世借口“千载难逢的机会”向塞尔维亚宣战。这个“机会”是指( )
When he was running after his brother, the boy lost his ___ and had a bad fall.
已知2x+5y=3，求4x•32y的值．
物体的动量变化量的大小为5kg•m/s，这说明（ ）
