甲、乙两人独立地解同一问题,甲解决这个问题的概率是p1,乙解决这个问题的概率是p2,那么恰好有1人解决这个问题的概率是( )
我国多数野生生物濒危或灭绝的主要原因是( )
— What would you send to your sister as the Christmas gift?
— I haven't decided yet. I ________ send her a handbag.
圆x2+y2-2x+2y=0的周长是( )