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

蒙古族忌讳坐蒙古包的( )角。

A．东北
B．西北
C．东南
D．西南