Which of the following must use the accrual method of accounting?

I.	A property management company, operating as a C corporation, with average annual gross receipts of $50,000,000.
II.	An incorporated law firm with average annual gross receipts of $50,000,000.
III.	An unincorporated grocery store with average annual gross receipts of $50,000,000.

a. All of these must use the accrual method.

b. None of these choices must use the accrual method.

c. Only I and III must use the accrual method.

d. Only I and II must use the accrual method.