这几个模型的区别可以详细讲下吗

问题如下：

Which method is to estimate default risk that considers volatility, credit scores, and comparisons to similar borrowers to enhance predictions?

选项：

A.

Merton model.

B.

Credit Risk+ model.

C.

Credit Metrics model.

D.

KMV model.

解释：

The Credit Metrics model is the option for peer comparisons. It considers bond issuer credit ratings (unlike the Credit Risk+ model). The Merton model uses option pricing theory to calculate the default rate, but it only considers shortterm debt. Moody’s-KMV model adds some long-term debt to the theory behind the Merton model, but the CreditMetrics model is the best option due to peer comparison demands.