Final answer:
The Dow Jones Industrial Average is the narrowest measure of the market as it is comprised of only 30 large U.S. companies, providing a concentrated view compared to broader indices.
Step-by-step explanation:
The narrowest measure of the stock market among the options provided is D. the Dow Jones Industrial Average (DJIA). The DJIA is a price-weighted average that tracks 30 large publicly-owned companies trading on the New York Stock Exchange (NYSE).
In contrast, broader measures such as the S&P 500 Index track the stock prices of 500 large companies, and the Wilshire 5000 includes a far larger number, covering nearly the entire market of publicly-traded U.S. companies. Thus, with only 30 companies, the Dow Jones Industrial Average provides the most concentrated snapshot of market performance, making it the narrowest index listed.