What aspect of insurable risk refers to the idea that risks must be large enough to predict losses accurately?

The aspect of insurable risk that involves risks being significant enough to allow for the accurate prediction of losses is fundamentally tied to the Law of Large Numbers. This principle in statistics suggests that as the number of exposure units increases, the actual loss experiences will get closer to the expected loss. In insurance, this means that a larger pool of policyholders helps insurers more reliably predict overall losses.

By gathering a vast amount of data and experiences over time, insurance companies can create more stable estimates for their premiums and are better prepared to cover claims. The Law of Large Numbers enables insurers to manage risk effectively, leading to sound financial practices.

Other aspects provided in the choices, such as definable risk, adequate premiums, and exclusions, address different areas of insurance concepts but do not specifically pertain to the prediction of losses based on the size of the risk pool like the Law of Large Numbers does.