A:I'm going to Dalian.
B:In August.
C:I've been to England.
A
B
C
D
化学式
CH4
(甲烷)
C2H6
(乙烷)
C4H10
(丁烷)
C6H14
(己烷)
沸点/℃
﹣160
﹣88
﹣0.5
69
设函数fx=2a-1x+b是R上的减函数,则有( )