(A)2b>2a>2c (B)2a>2b>2c (C)2c>2b>2a (D)2c>2a>2b
A
解析:∵函数在(0,+∞)上是单调递减函数,
∴b>a>c>0.
又∵函数y=2x在R上是增函数,
∴2b>2a>2c.故选A.