货币之所以能充当价值尺度，从根本上说是因为( )。

A．货币本身是商品，它具有价值

B．货币是财富的象征

C．货币本身是劳动产品

D．货币有其特殊的使用价值

I have got used to staying up late at night        I'm really tired and want to go to sleep early. [ ]

A. unless

B. if

C. and

D. or