A.2^b>2^a>2^c                   B.2^a>2^b>2^c

C.2^c>2^b>2^a                   D.2^c>2^a>2^b

已知

則=

  (A)        (B)               (C) 1            (D) 0

已知,則(    )

A.2^b>2^a>2^c                                   B.2^a>2^b>2^c

C.2^c>2^b>2^a                                   D.2^c>2^a>2^b

已知 則=

A．；B．；C．；D．

已知則(  )

A.               B.              C.             D.