The cleveland massacre was
a takeover by standard oil of the refineries in cleveland.
a labor dispute at standard oil in cleveland that turned violent.
an attempt to stop standard oil from becoming a monopoly.
a failed attempt by standard oil to take over other refineries.

The correct answer is: The Cleveland Massacre was  a takeover by Standard Oil of the refineries in Cleveland.

Rockefeller spoke personally with the competitors of Standard Oil in Cleveland, to make them an offer that the refineries could not refuse.

In this way, he bought a large part of the Cleveland refineries and positioned himself for national control of the oil industry.  His victory was called the "Cleveland Massacre."

The Cleveland Massacre was  a takeover by Standard Oil of the refineries in Cleveland.

Explanation:

In 1870 Standard Oil was one of the largest refineries in the Midwest of the United States and already in 1872, along with two of the most important refiners in Pittsburgh and Philadelphia, they could handle rail rates at their whim. Standard Oil refined a quarter of all the country's oil production, and by eliminating competition step by step, it became a powerful monopoly that refined 95% of the country's total capacity.  

At the beginning of 1872, Rockefeller was determined to finish his project of taking over the oil industry, for which he advanced, giving an unprecedented maneuver, helping to create the South Improvement Company, an association that included the main petroleum refiners of Cleveland, reaching agreements with railway companies to obtain significant discounts for members of the association. This agreement caused the claim of the public that advocated its cancellation, something that was achieved legally, three months later, before the protests of the people, but by then almost all of Rockefeller's competitors had been forced to sell or to associate with him. In a matter of three months, Rockefeller had bought 22 of the 25 refineries in Cleveland, all thanks to this magnificent maneuver, passing that feat to be called the "Massacre of Cleveland."

what are local authorities doing to fix the problem

explanation:

electricity

so thats all folks