Answer:
d. are average stock prices for a group of companies meant to measure a section of the stock market.
Explanation:
Stock indices are used to measure the performance of a basket of securities and helps investors in a particular segment of the financial market make well informed decisions.
The value of the index is an average of the stock of underlying companies that make up the index.
For example the Dow Jones is a stock index made up of 30 large companies.
Investors compute performance by comparing current price level to previous prices.