Which of the following is(are) true regarding cost flow assumptions?

A. Manufacturing firms are required to use FIFO.

B. Service firms are required to use LIFO.

C. If a firm uses FIFO for tax purposes, then FIFO must be used for financial reporting purposes.

D. If a firm uses LIFO for tax purposes, then LIFO must be used for financial reporting purposes.

E. All of the above.