Which statement about the LIFO inventory valuation method is true?

a. LIFO liquidations occur when units purchased exceed units sold.

b. LIFO gives a current valuation for ending inventory on the balance sheet.

c. A LIFO layer is a group or block of units purchased at a certain unit cost.

d. The LIFO conformity rules states that if LIFO is used for financial statements, it must be used for tax returns.