An insured can increase the monthly benefits paid under a disability income policy by a specified percentage or in relation to an economic index with which of the following riders?

The future income option rider provides the insured with the ability to purchase additional coverage at a later date without undergoing medical underwriting. While it allows for the potential increase in coverage, it does not automatically adjust benefits based on inflation or economic changes, which is the primary function of the cost of living adjustment rider.

This rider refunds the premiums paid into the policy if no claims are made during the policy term. While it offers a financial benefit if the insured does not use the policy, it does not modify the monthly benefits or provide increases related to inflation or economic indices.

Income replacement refers to the primary function of disability income policies, which is to replace lost income due to an inability to work. However, it does not involve increasing the benefit amounts over time or in relation to any economic indicators, making it unrelated to the question of increasing benefits through a rider.