15. In pension accounting, the employer's net pension liability: A. Is measured as the total pension liability less the amount of fiduciary net position held for future pension payments. B. Represents the portion of the present value of projected benefit payments to be provided through the pension plan to current active and inactive employees that is attributed to those employees' past periods of service. C. Is the same as the net pension obligation. D. Is based on actuarial valuations generally required to be performed at least every five years