Which of the Following Is a CORRECT Statement About Asset

Which of the following is a CORRECT statement about asset impairment?

A) An asset is impaired if the net book value is less than the expected future cash flows.
B) If an asset is impaired, the expected future cash flows will exceed the net book value.
C) Under U.S. GAAP, an asset that has been written down because of impairment can be written back up if it increases in value in the future.
D) If an asset is impaired, the impairment loss is the difference between the net book value and the fair value.