Read the excerpt from ida tarbells the history of the standard oil company:

"he [rockefeller] meant to control the oil business. by one maneuver, and that a discredited one, he had obtained control of one-fifth of the entire refining output of the united states. he meant to secure the other four-fifths. he might retire now, but the oil region would hear of him again. it did. three months later, in august, 1872, it was learned that the scheme of consolidation which had been presented in vain at titusville in may had been quietly carried out, that four-fifths of the refining interests of the united states . had gone into a national refiners association, of which mr. rockefeller was president.

what is tarbell accusing rockefeller of doing?
a. ignoring the sherman act
b. trying to create a monopoly
c. price-fixing
d. stealing oil