∵y=( 

1

2

) x是单调递减函数且x＜y∴(

1

2

)x＞(

1

2

)y排除A

∵y=x-

1

3

在x＞0时单调递减且0＜x＜y∴x-

1

3

＞y-

1

3

排除B．

y=log₂x单调递增且0＜x＜y∴log₂x＜log₂y∴

1

2

log2x＜

1

2

log2y∴log2x

1

2

＜log2y

1

2

故C对．

故选C．