How does the amortization of tax-deductible goodwill affect the computation of a parent company’s income taxes?

  a. It is a deductible expense only if the parent owns at least 80 percent of subsidiary’s voting stock.
  b. It is deductible only as impairments are recognized.
  c. It is a deductible item over a 15-year period.
  d. It is deductible only if a consolidated tax return is filed.