某商业银行当年将100个客户的信用等级分为BB级，该评级对应的平均违约概率为1%；第二年观察这组客户，发现有4个客户违约，则该客户的违约概率为（）。

A．1%

B．2%

C．3%

D．4%

An analyst does research about required rate of return. With respect to an investor's required rate of return, those components included in the nominal riskfree rate of return will most likely:

A. affect all of the investments.
B. be relatively constant over time.
C. affect the yield spread between government securities and corporate securities.