What Is the Major Difference Between a Periodic and Perpetual

What is the major difference between a periodic and perpetual inventory system?

A) Under the periodic inventory system,the purchase of inventory will be debited to the Purchases account.
B) Under the periodic inventory system,no journal entry is recorded at the time of the sale of inventory for the cost of the inventory.
C) Under the periodic inventory system,all adjustments such as purchases returns and allowances and discounts are reconciled at the end of the month.
D) All of the answers are correct.