Explanation:

Cross-sectional anomalies refer to patterns that exist across different stocks or securities at a given point in time. These anomalies involve differences in returns based on certain characteristics or factors.

Value effect is a classic cross-sectional anomaly where value stocks (stocks with low price-to-book ratios, low price-to-earnings ratios, or high dividend yields) tend to outperform growth stocks over time. This anomaly compares different types of stocks at the same point in time.

Overreaction effect is a time-series anomaly that relates to how stock prices react to news over time - typically prices overreact to new information and then correct themselves over subsequent periods.

Closed-end fund discount is also a time-series anomaly that refers to the tendency of closed-end funds to trade at prices different from their net asset values, which may vary over time.

Therefore, among the options provided, the value effect is most clearly a cross-sectional anomaly as it involves comparing different types of stocks based on their characteristics at a given point in time.