Benchmark Selection for Large-Cap U.S. Equities

Jessica is a portfolio manager who is evaluating the performance of her investment fund over the past year. She is considering how best to benchmark her fund's performance to ensure that she has an accurate measure of her investment strategy's success. A benchmark is crucial for evaluating whether the returns generated by a portfolio are adequate relative to the market or segment it is intended to represent.

What is the most appropriate benchmark for Jessica's investment fund if it primarily focuses on large-cap U.S. equities?