Final answer:
The mandatory feature of a high-deductible health plan (HDHP) is a Health Savings Account (HSA), which is a tax-advantaged account that pairs with an HDHP and is owned by the individual. The correct answer is D) Health savings account (HSA).
Step-by-step explanation:
The question asks which of the following is a mandatory feature of a high-deductible health plan (HDHP). Among the options given, the correct answer is D. Health savings account (HSA). A high-deductible health plan typically pairs with an HSA, which is a tax-advantaged medical savings account available to taxpayers in the United States who are enrolled in an HDHP. The funds contributed to an HSA are not subject to federal income tax at the time of deposit.
HSAs are owned by the individual, which differentiates them from company-owned Health Reimbursement Arrangements (HRAs) that are an alternative and cannot be mandatory for HDHPs. Furthermore, options A and B, which refer to the option to enroll in a vision or dental plan, are not mandatory features of an HDHP. So, the correct answer is D) Health savings account (HSA).