--- This history book is of great value.

--- Exactly. ____________ can be enjoyed from it ____________ you have a deep understanding of it, however.

A．Nothing; unless

B．Few; till

C．Something; until

D．Little; since

以葛根汤主治的"欲作刚痉"，提示因邪阻筋脉，势将强急成痉之兆的症状是（）

A.项背强几几

B.身体强几几

C.口噤不得语

D.脚挛急