What is an open-ended investment company primarily managed by an insurance company called?

An open-ended investment company primarily managed by an insurance company is called a Separate Account. This structure allows an insurance company to manage assets separately from its general account, providing additional investment options for policyholders, particularly in variable insurance products.

These Separate Accounts are typically used in variable life insurance and variable annuity products, where the investment performance of the separate accounts directly affects the policyholder's cash value and death benefits. The design allows for flexibility in investment choices, as the policyholder can usually select among various investment options within the Separate Accounts.

The other options pertain to different types of investment vehicles. A Mutual Fund is a pooled investment vehicle that is not necessarily linked to insurance products. A UIT, or Unit Investment Trust, is an investment company that offers a fixed portfolio of securities and has a limited lifespan. An Exchange-Traded Fund (ETF) is similar to mutual funds but trades on stock exchanges like individual stocks. Understanding the unique attributes of each helps clarify why the correct answer is specifically a Separate Account when it comes to open-ended investment companies managed by insurance firms.