Question

How did John D. Rockefeller horizontally integrate his monopoly in 1882?
He purchased iron mines around the country to add to his business.
He created a trust that controlled oil wells, refineries, and distribution networks.
He created a trust that controlled ninety percent of the nation's oil refineries.
He purchased coal plants around the country to add to his business.

Answer 1

He created a trust that controlled ninety percent of the nation's oil refineries.

The 1882 Standard Oil Trust consolidated many competing refineries under a single management, which is horizontal integration (controlling competitors at the same production level).