When the Periodic Inventory System Is Used

When the periodic inventory system is used:

A) operating profit from the sale of an item from inventory is known when the item is sold.
B) gross profit from the sale of an item from inventory is known when the item is sold.
C) cost of goods sold can be calculated by subtracting the ending inventory amount from the sum of beginning inventory and net purchases.
D) a physical inventory must be taken in order to estimate the cost of goods sold.