Which of the following statements is correct?

a. A calendar year corporation must file its tax return no later than March 15 unless it requests an extension.

b. A corporation is a legal entity that is taxed on its taxable income.

c. Corporations choose their tax year in their first year of operation and can elect to change it in their third year of operation.

d. Large corporations without inventory can choose to use either the cash or accrual method of accounting.