Which business practice did rockefeller repeatedly use that him succeed in building his oil monopoly?

He monopolized oil so that no one else could compete with his businesses. There was so controversial "cheating" involved but it doesn't really matter, he gave most of his wealth to charity.
Hope this helps!

Rockefeller can be noted for using the controversial business practice of monopolization which helped him build his oil business :)

Americans often speak of their country as one of several large regions.  these regions are cultural units rather than governmental units --  formed by history and geography and shaped by the economics, literature and folkways that all the parts of a region share. what makes one region different from another? a region's multicultural heritage as well as distinct demographic characteristics like age and occupation make regions different and special. within several regions, language is used differently and there are strong dialects. there are also differences in outlook and attitude based on geography.