From which type of company has Frank purchased his automobile policy if he receives dividends as a stockholder?

The correct answer indicates that Frank has purchased his automobile policy from a stock insurer. A stock insurer is a type of insurance company owned by shareholders, who have invested capital into the company. These shareholders are entitled to receive dividends when the insurer has profitable operations. This aligns with the hint provided in the question that Frank receives dividends as a stockholder.

In contrast, a mutual insurer is owned by its policyholders, meaning that dividends are paid out to policyholders rather than shareholders. This can lead to confusion, but it's important to identify that dividends in the context of stock ownership are characteristic of stock insurers.

Reciprocal insurers operate on the concept of policyholders mutually agreeing to share risks, and profits do not arise from shareholders gaining dividends but rather through mutual agreements among the insured parties. A re-insurer, on the other hand, deals primarily with risk management for other insurance companies, not individuals, and does not issue direct policies to the general public.

Thus, the ability of Frank to receive dividends as a stockholder firmly indicates the type of company he has obtained his automobile policy from is indeed a stock insurer.