Which of the following statements is true?

A$.$ The performance of the U$.$S$.$ stock market is often measured by market indexes, which are averages of stock prices.

B$.$ The three most important indexes are the Dow Jones Industrial Average, the S&P $500,$ and the Nasdaq Composite Index.

C$.$ The S&P $500$ is composed of the stocks of the $500$ largest companies, so it does the best job of reflecting general movements in stock prices.

D$.$ All of the above.