Answer:
At the end of the accounting period,an adjustment causing a decrease in the liability account and an increase in revenue account is required
Explanation:
When advance payment is received from a customer,the fact that the payment is not due and that the seller has not earned means it should be posted to a liability account,revenue prepayment account.
At the end of the period,when a part or all of the revenue is earned , an adjusting entry is required to reclassify the amount from the liability account to a revenue account, that way, amount shown as liability reduces and the revenue increases.