Which statement regarding goodwill is true?

a. Goodwill is an unidentifiable intangible asset.

b. Internally developed goodwill should be capitalized while purchased goodwill should be expensed.

c. goodwill can be defined as the value attached to the ability of a company to earn a higher than normal rate of return on the book value of its identifiable assets.

d. In some situations, GAAP and IFRS requires that negative goodwill be recorded.