Which of the following statements is/are correct?

a. Private foundations must file Form 990-PF (Return of Private Foundation).

b. If an exempt organization records annual gross receipts of less than $50,000, it files Form 990-N.

c. An exempt organization with less than $250,000 in gross receipts may file a Form 990-EZ.

d. Only "If an exempt organization records annual gross receipts of less than $50,000, it files Form 990-N" and "Private foundations must file Form 990-PF (Return of Private Foundation)" are correct.