If no legal, regulatory, contractual, competitive, economic, or other factors limit the life of an intangible asset, the asset’s assigned value is allocated to expense over which of the following?

  a. 20 years.
  b. 20 years with an annual impairment review.
  c. Infinitely.
  d. Indefinitely (no amortization) with an annual impairment review until its life becomes finite.