Which of the following statements about intangible assets is TRUE? a. Intangible assets purchased from another entity must be amortized over 20 years. b. GAAP rules prevent internally developed intangible assets from being reported on the balance sheet. c. Intangible assets can be classified as either current or long-term assets. d. Natural resources, such as oil and gas, are intangible assets that are adjusted annually for impairment. Answer C above is true Answer D above is true Answer B above is true Answer A above is true