In a perpetual inventory system, when inventory is purchased on account, the appropriate journal entry would involve debiting the Merchandise Inventory account and crediting the Accounts Payable account. This reflects the increase in inventory and the obligation to pay for that inventory later.
Therefore, the correct entry for recording the purchase of inventory on account for $12,000 is:
B.
Merchandise Inventory
$12,000
Accounts Payable
$12,000