C is corrent. ROI is equal to net operating profit divided by invested capital. Therefore, it is equal to 15% (3,000,000 ÷ 20,000,000).
A is incorrect because ROI is equal to net operating profit divided by invested capital.
A is incorrect because ROI is equal to net operating profit divided by invested capital.
D is incorrect because ROI is equal to net operating profit divided by invested capital.