eturn on investment $($ROI$)$ is commonly expressed in each of the following ways, except Blank$\_\_\_\_\_\_.$

Multiple choice question.

ROI $=$ Net income $/$ Average total assets

ROI $=$ Operating income $/$ Average operating assets

ROI $=$ Net income $/$ Average stockholders' equity

ROI $=$ Net income $/(($Beginning of year total assets $+$ end of year total assets$)/2)$