Ras蛋白是如何激活的？

腰俞麻醉的解剖标志是（）

A.第二骶骨棘突

B.第三骶骨棘突

C.第四骶骨棘突

D.骶骨角

E.骶裂孔

哪些是产生压力的因素()

A．心理因素

B．生物因素

C．生理因素

D．化学因素

E．物理因素

用大枣最多的方剂是（）

A.苓桂枣甘汤

B.十枣汤

C.当归四逆汤

D.桂枝汤

E.炙甘草汤

无效合同就是没有法律效力的合同。

Which of the following statements regarding the term structure of interest rates is least accurate（）

A. Under the market segmentation theory, a flat yield curve is likely to become positively sloped if the demand for long-term bonds exceeds supply and if the supply of short-term bonds exceeds demand.

B. Forward interest rates are the best estimates of future short-term interest rates under the pure expectations theory.

C. The observed yield curve likely contains elements of liquidity preference, market segmentation, and expectations theories.