请问这道题是什么意思？为啥这样做？

问题如下：

Stratton’s estimated conglomerate discount just prior to the announcement is:

选项：

A.

–USD17 billion

B.

USD0

C.

USD17 billion

解释：

C is correct. The estimated conglomerate discount just prior to the announcement is calculated as follows: Total estimated enterprise value from sum-of-the-parts valuation – Current trading enterprise value = USD187 billion – USD170 billion = USD17 billion.

A is incorrect because it incorrectly subtracts the estimated enterprise value from the current trading enterprise value.

B is incorrect because the estimated and current trading enterprise values are not equal.