把2xy﹣x2﹣y2分解因式，结果正确的是[ ]
A．（x﹣y）2
B．（﹣x﹣y）2
C．﹣（x﹣y）2
D．﹣（x+y）2
答案：C
It’s helpful to put children in a situation they can see themselves differently.
A．that
B．when
C．which
D．where
泡沫枪PQ8的主要性能如何？
