The auditor performs analytical review procedures and discovers an unexpected increase in the ratio of gross profit to sales (gross margin percentage). The client takes an annual physical inventory and adjusts the inventory amount based on the physical inventory at year-end in December. An error that could explain the decrease in gross profit is. O The client lost several inventory tags resulting in an understatement of ending inventory. OA January sale recorded in Decemberuary. OA change in sales mix that increased the percentage of sales from low margin items. OA January purchase recorded in December.