选项B 是个什么意思啊 请老师解答

问题如下：

Ace bank is considering buying the super-senior tranche [10%$—$12%] of a synthetic collateralized debt obligation (CDO). The pricing of the tranche assumes a fixed recovery of 50% for all names. All else remaining equal, which one of the following changes will make the principal invested less risky?

选项：

An decrease in subordination of 1% (i.e., investing in the [9%—11%] tranche)

An decrease in the tranche thickness from 2% to 1% (i.e., investing in the [10%—11%] tranche)

Using a recovery rate assumption of 40%

An decrease in default correlation between names in the portfolio.

解释：

D is correct.

考点：CDO

解析：

A is incorrect. Decreasing the subordination will make the senior tranche more risky because there is a thinner layer beneath to absorb losses.

B is incorrect. Decreasing the thickness of the tranche will make it more likely to be wiped out.

C is incorrect. An decrease in recovery rate will make it more risky.

D is correct. An decrease in the default correlation will decrease the risk.