问题如下：
Which of the following descriptions most accurately describes the IRR and NPV methods?
选项：
A.A project’s IRR must be negative when the NPV is negative.
B.A project with an IRR equal to the cost of capital will have an NPV of zero.
C.A project’s NPV may be positive even if the IRR is less than the cost of capital.
解释：
B is correct.
A project’s IRR can be positive even if the NPV is negative.A project will have a negative NPV if its IRR is less than the firm’s cost of capital.
老师，请问关于C选项，如果现金流出现正负不等的情况，也有可能R有两重取值，如果R取值是负的话，那么R肯定是小于capital cost 的，这个时候的R对应的NPV 也是等于0呢，所以C为什么不对呢？
