Answer:D.The efficiency with which a firm utilizes its assets
Explanation:The efficiency with which a firm utilizes its assests would be the most difficult to assess.
The efficiency ratio is determined by the company's ability to effectively and adequately uses its assests and also manage its liabilities during a specific period of time.
Efficiency ratio comprises of inventory turnover ratio, receivables turnover ratio and assets turnover ratio. The mentioned ratio measure how efficiently a company utilizes its in revenue generation and its capability to effectively manage those assests.