A financial services company is considering investing in a new fintech startup that has developed a new technology platform for investment management. The company is concerned about the risks associated with the investment and wants to evaluate the potential return on investment. You have been hired as a consultant to help the company make an informed decision. Which of the following financial ratios would be most appropriate for the financial services company to evaluate the financial health and performance of the fintech startup?

Gross profit margin

Price$-$to$-$earnings $($P$/$E$)$ ratio

Return on investment $($ROI$)$

Debt$-$to$-$equity ratio