答案能再解释一下吗？

问题如下：

Your colleague is building financial statement and discounted cash flow models for a company and has asked you review their modeling decisions with respect to the subject company’s post-employment and stock-based compensation plans.

Your colleague’s discounted cash flow model expenses service cost and net interest expense in free cash flow and deducts the company’s net pension liability from enterprise value to arrive at an estimate of equity value. You most likely recommend that your colleague:

选项：

A.

make no changes.

B.

remove service cost from free cash flow because it is a non-cash expense.

C.

remove net interest expense from free cash flow because the net pension, at present value, is already deducted from enterprise value.

解释：

C is correct. Net interest expense for a DB plan represents the unwinding of the discount with the passage of time. The discounted cash flow model values a company at the present time. Service cost is correctly expensed in the model as it represents increases in the pension obligation unrelated to the time value of money.