Which of the following statements is incorrect regarding the taxation of C corporations for tax years beginning after 2017?

a. NOLs are subject to a 2-year carryback and 20-year carryforward period. TRUE

b. Taxable income of a personal service corporation is taxed at a flat rate of 21%. TRUE

c. A tax return must be filed whether or not the corporation has taxable income. TRUE

d. The alternative minimum tax does not apply.

e. None of these.