John D. Rockefeller created a monopoly with his control of oil in America. He dropped oil prices lower than cost and put his competitors out of business. Then bought all of his competitors out. How did Rockefeller control the oil market? A. Horizontal Integration
B. Vertical integration
C. Civil action court
D. Sherman Antitrust​

the great wall of china worked as a defense for the feudal states of the zhou dynasty to the north. during the warring states period more walls were put up to defend the borders of the different kingdoms. it was semi successful because despite the wall, the mongols eventually conquered china also the great wall provided protection to the economic development and cultural progress, safeguarded the trading routes such as the silk road, and secured transmission of information and transportation. @jayxboof