A:It doesn’t matter
B:It’s up to you
C:Don’t mention it
D:That’s all right
下列分子晶体:
①HCl ②HBr ③HI ④CO ⑤N2 ⑥H2
熔、沸点由高到低的顺序是( )
解方程组:x+2y=33x-y=2