Which provision limits income benefits based on the insured's income from the past two years?

The provision that limits income benefits based on the insured's income from the past two years is the "Relation of earnings" provision. This provision is essential in disability insurance, as it helps determine the amount of benefits an insured individual can receive when they become disabled and are unable to work.

The "Relation of earnings" provision typically calculates the maximum benefit based on the insured's average income over a specified period, often the past two years. This ensures that the income benefits remain aligned with the insured's actual earning capacity and financial needs prior to the disability. By using historical income data, the insurance company can set appropriate benefit levels that reflect what the insured would likely have earned if they had not become disabled.

The other options serve different functions related to health and accident insurance. An impairment rider generally provides coverage specifically for certain losses or disabilities but does not focus on income from previous years. The future increase option allows insureds to increase their coverage amounts in the future without needing to provide additional evidence of insurability, which is not about past earnings. A cost of living adjustment (COLA) is designed to adjust benefits for inflation or changes in the cost of living but does not relate directly to the insured's historical income.