Explanation:

The correct answer is A. Style index because style indexes categorize securities based on market capitalization, along with other characteristics like growth or value. These indexes are designed to mirror the investment styles of specific investors, such as growth, value, or small-cap investors.

• B. Sector index is incorrect because sector indexes track different economic sectors (e.g., consumer goods, energy, finance) on a national, regional, or global basis, not market capitalization.

• C. Multi-market index is incorrect as these indexes represent multiple national markets, geographic regions, or economic development groups, rather than focusing on market capitalization classifications.