聚四氟乙烯在415℃以上急剧分解，并放出有毒的全氟异丁烯气体。( )
参考答案：错
若实数x,y适合不等式xy>1,x+y≥-2,则 ( )
A．x>0,y>0
B．x<0,y<0
C．x>0,y<0
D．x<0,y>0
—__________do you go to see your uncle?
—Three times a month.
A．How long
B．How many
C．How often
D．How old
