Q4.13: salaries and wages expense should have been accrued on december 31st, but the entry was not made. the result of this oversight is that

The answer to the given situation is "the result of this oversight is that the liabilities are understated".
We can define understated as if someone say to you that your account is understated, it means that either the amount is incorrect or the amount is too small or it is less than the actual or true amount. In the given case the entry was not made due the understatement of liabilities.