The correct answer is A) British Legislature.
The best definition for the underlined term based on the following sentence: "Thomas Paine argues that Parliament has established unfair laws against the colonists" is British Legislature.
The British Parliament has three areas: the House of Commons, the House of Lords, and the Monarchy, represented by Queen Elizabeth. The main responsibilities of the British Parliament are overseeing the work of the Primer Minister and the government, create or change laws, and the debate of legislation that benefits citizens of the United Kingdom.