Final answer:
Horizontal integration is the business method that allowed companies during the Industrial Revolution to control market share, as exemplified by John D. Rockefeller's strategy in the oil industry.
Step-by-step explanation:
The business method used during the Industrial Revolution that would allow a company to control the market-share of a specific product is horizontal integration. This practice involves a company acquiring other companies that operate at the same level in the industry, which is precisely what John D. Rockefeller did with his Standard Oil Company. Through horizontal integration, he merged with other oil companies or underpriced his competition to drive them out of the market, eventually allowing him to dominate the oil industry and set prices to his advantage.