Which of the Following Statements Is True Concerning Accounting Estimates

Which of the following statements is true concerning accounting estimates?

A) Accounting estimates are a fundamental and necessary aspect of many accounting measurements.
B) In many situations, making good estimates requires a company to hire third-party estimates who have expertise in the area being measured.
C) In order to maintain accounting independence, estimates should made by personnel outside of the accounting function.
D) Accounting estimates are inherently difficult to make.