Additional metrics might include which of the following?

The choice that includes the length of rental, number of rentals, and returns is correct because these metrics provide valuable insights into the operational performance of a rental business. They help in assessing how efficiently the business is operating by analyzing the usage patterns of rental items.

Tracking the length of each rental allows the business to evaluate the average duration customers keep the rentals, informing inventory management and pricing strategies. The number of rentals gives an overview of the demand for the services offered, reflecting customer preferences and seasonal trends. Additionally, monitoring returns can highlight customer satisfaction and the condition of rental items, which is crucial for maintaining quality service and optimizing inventory turnover.

In this context, all of these metrics combine to create a detailed picture of the rental operation's effectiveness and can guide strategic decisions to improve performance further. Other options, while potentially providing important information, do not encompass the same operational insights specific to the rental business model as effectively as the metrics in the correct choice.