U. S. Treasury securities face several risks to varying degrees. Generally speaking, rank the following risks that an investor in a 5 percent coupon, 25-year, off-the-run U. S. Treasury bond, issued after 1984, would face. Order them from left to right with the least likely risk first through the most likely risk faced by the investor last. 1=liquidity risk. 2=prepayment risk. 3=default risk. 4=interest rate risk.（）

A. 1, 2, 3, 4.

B. 2, 3, 1, 4.

C. 4, 3, 1, 2.

缓冲溶液能够对抗外来少量强酸强碱的原因，错误的是（）

A.多元酸的酸式盐及其对应的次级盐，弱碱及其对应的盐，弱酸极其对应的盐所组成的缓冲溶液的作用机制相似

B.以醋酸一醋酸钠缓冲系为例，NaAc是缓冲溶液的抗酸成分

C.以醋酸一醋酸钠缓冲系为例，HAc是缓冲溶液的抗碱成分

D.缓冲作用是有一定限度的，一旦强酸、强碱量过大，缓冲溶液将丧失原有缓冲能力

E.起到缓冲作用的两种以上的组成成分都可以组成缓冲溶液