Benchmark Selection for Large-Cap Equity Portfolio

A portfolio manager is responsible for evaluating the performance of a portfolio of investments. The manager is considering three potential benchmarks to assess the portfolio's performance. The portfolio consists primarily of large-cap U.S. equities, while the three benchmark options proposed include:

1. The S&P 500 Index

2. A custom index consisting of only the portfolio's top 10 holdings

3. A blended index of U.S. large-cap and small-cap stocks

Which of these benchmarks would be the most appropriate for performance evaluation of the portfolio?