问题如下：
Which of the following statements best describes the calculation of implied correlation?
选项：
A. The implied correlation for the
mezzanine tranche assumes non-constant pairwise correlation.
B. Observable market prices of credit
default swaps are used to infer the tranche values.
C. The tranche pricing function is
calibrated to match the model price with the market price.
D. The risk-adjusted default
probabilities are used in model calibration.
解释：
C Starting with observed market prices and a pricing function for the tranches, it is possible to back out the implied correlation to calibrate the model price with the market price. The computation of implied correlation assumes constant pairwise correlation. Both credit default swap and tranche values are observed. Observed tranche values are used in conjunction with risk-neutral default probabilities to compute implied correlation.
怎么感觉ABCD都是对的，能分别说说不对的选项错在哪里么？总觉得每个单词都认识，但是合在一起就不知道讲什么，这是我常常做不对这种题的原因，该如何改善这种情况呢？
