Which of the Following Is Correct About Goodwill Impairment

Which of the following is correct about goodwill impairment?

A) The fair value of the investee company is compared with the fair value of the investor's equity investment account.
B) If the fair value is less than the investment balance, the investment is deemed impaired.
C) If the book value is less than the investment balance, the investment is deemed impaired.
D) The future expected cash flows of the investment are compared with the book value of the investment.