Which of the following combinations plans is designed to protect an insurer from an unpaid mortgage balance upon death?

The option that best protects an insurer from an unpaid mortgage balance upon death is the joint life insurance plan. This type of policy covers two individuals, typically spouses, and pays out a death benefit upon the death of the first insured. In scenarios where a mortgage is involved, if one spouse passes away, the policy can provide the necessary funds to pay off the mortgage, ensuring that the surviving spouse is not burdened by the debt.

The structure of joint life insurance serves not only to protect the insurer against potential losses, but it also offers financial security to families who may face the sudden loss of income that could impact their ability to maintain mortgage payments. Therefore, it's an effective planning tool for households that have significant mortgage obligations.

Term life insurance, while it provides a death benefit for a specified term, does not inherently ensure mortgage protection unless explicitly designed for that purpose. Whole life and universal life insurance are permanent policies that accumulate cash value but do not specifically address the mortgage balance in the same way that a joint life plan can. Thus, joint life insurance is the chosen option for addressing the concern of an unpaid mortgage balance upon the death of an insured individual.