Why Are Laws Aimed at Regulating Monopolies Called "Antitrust" Laws

Why are laws aimed at regulating monopolies called "antitrust" laws?

A) The rise of large firms (e.g., Standard Oil) in the late 1800s in the United States caused consumers to lose trust in private business.
B) "Trust" was a word in Old English that meant monopoly in the Middle Ages. Therefore, "antitrust" is a term that means "against monopoly."
C) In the late 1800s, firms in several industries formed trusts; the firms were independent but gave voting control to a board of trustees. Antitrust laws were passed to regulate these trusts.
D) In the late 1800s, firms in several industries formed trusts; they were called "trusts" because when corporate officials were questioned about their business they would claim that business was good for the country and that they should trusted.