[单项选择题] Specific duties are levied ______ some physical unit such as dollars per bushel, per kilo, o

[单项选择题] Specific duties are levied ______ some physical unit such as dollars per bushel, per kilo, or per metre and ad valorem duties are calculated as a percent of the value of the goods.

A．on the basis of

B．with the basis of

C．on the base of

D．with the base of