Answer: Assuming perfectly liquid markets.

## Explanation **Model error** refers to flaws in the fundamental assumptions or structure of a financial model that can lead to inaccurate predictions or risk assessments. Let's analyze each option: - **A. Assuming a non-normal distribution of returns**: This is actually a more realistic assumption than assuming normality, as financial returns often exhibit fat tails, skewness, and other non-normal characteristics. This represents model improvement rather than error. - **B. Assuming perfectly liquid markets**: This is a classic model error. In reality, markets are not perfectly liquid - there are transaction costs, bid-ask spreads, and liquidity constraints. Assuming perfect liquidity can significantly underestimate trading costs and execution risk, especially during stress periods. - **C. Assuming variable distribution of asset price**: This is actually a more sophisticated approach that acknowledges changing market conditions, rather than a model error. - **D. Assuming imperfect capital markets**: This is a more realistic assumption that accounts for market frictions, making it less of a model error. **Therefore, option B is the best example of a model error** because assuming perfectly liquid markets ignores real-world market frictions and can lead to substantial underestimation of trading costs and liquidity risk.

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