--- Can I help you ?

    --- I’d like to buy a present for my best friend, _______at proper price but of great use.

A．that

B．one

C．it

D．this

治疗"大风四肢烦重"中恶寒不足者"，宜用（）

A.侯氏黑散

B.风引汤

C.两者皆可

D.两者皆非