The Gross Profit Method of Estimating Inventory Would Not Be

The gross profit method of estimating inventory would not be useful when

A) a periodic system is in use and inventories are required for interim statements.
B) inventories have been destroyed or lost by fire, theft, or other casualty, and the specific data required for inventory valuation are not available.
C) there is a significant change in the mix of products being sold.
D) the relationship between gross profit and sales remains stable over time.