Which benefit allows the insured to add additional life insurance at specific ages or milestones?

The correct answer is the benefit that allows the insured to add additional life insurance at specific ages or milestones, which is known as guaranteed insurability. This benefit enables policyholders to increase their life insurance coverage without undergoing additional medical underwriting at designated times in their lives, such as reaching a certain age or experiencing significant life events like marriage or the birth of a child. This feature is particularly valuable as it provides the insured with the opportunity to secure additional coverage based on their changing needs while protecting them from potential health changes that could affect their insurability later on.

In contrast, waiver of premium is a provision that allows the policyholder to skip premium payments if they become disabled, but it does not provide for an increase in coverage. Single premium payment refers to a policy where the entire premium is paid at once, rather than through a series of payments, but it does not pertain to adding coverage. Flexible premium payment involves the ability to adjust the amount and frequency of payments for certain types of policies but does not directly relate to the availability of additional coverage at specific milestones or ages.