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

I. A property management company, operating as a 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$.$ Only I and II must use the accrual method.

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

d$.$ None of these must use the accrual method.