Which of the following is a common form of policy benefit that is not guaranteed?

Policy dividends are a common form of policy benefit that is not guaranteed because they are based on the insurer's financial performance and are typically offered by participating whole life insurance policies. Policyholders may receive dividends depending on factors such as mortality rates, expense ratios, and investment returns, but these distributions can vary from year to year and are not promised in advance. The insurer's ability to generate excess profits beyond what is required to cover claims and operational costs ultimately determines the dividends declared.

In contrast, death benefits are generally guaranteed as they are a fundamental part of life insurance contracts, promising to pay a specified amount upon the insured's death. Insurance rider benefits can also be guaranteed depending on the type of rider and the terms agreed upon in the policy. Premium rebates, while sometimes offered as incentives, are not standard benefits and also do not guarantee payment. Thus, policy dividends stand out as the option that encompasses a benefit reliant on uncertain factors.