The risks of the overall market that can't be diversified by adding more stocks to a portfolio is called _____ risk.

The correct answer is systematic risk, which refers to the type of risk that affects the entire market or a large segment of the market, and cannot be eliminated through diversification. Systematic risk encompasses factors such as economic changes, political events, and natural disasters that have the potential to impact the overall market.

In investment theory, even if a diversified portfolio includes a wide variety of individual stocks, it remains exposed to systematic risk that arises from broader market movements. This means no matter how many stocks are added to a portfolio, the portfolio is still susceptible to changes in the overall economic environment that affect all investments.

Additionally, other types of risk mentioned do not fit this definition. Unsystematic risk, or specific risk, is associated with individual assets or companies and can be mitigated through diversification. Market risk can often be seen as synonymous with systematic risk, but systematic risk is the more precise term used to define the non-diversifiable risk inherent in the market as a whole. Thus, understanding systematic risk is crucial for managing investment portfolios effectively in the face of unpredictable market fluctuations.