This act made it illegal to buy up companies in the same industry to gain a competitive advantage. the sherman antitrust act the pendleton civil service act the spoils system act none of the above

The Pendleton Civil Service Act prohibited giving away positions solely on the basis of political affiliation- so it's not about companies! The "Spoils systems" was a name given to the practice that this act prohibited.

The correct answer is The Sherman Antitrust Act - this is the act that prohibited monopolies, which is what unfair advantage is also called!