The correct answer is:
U.S. Department of State
Explanation:
The executive department with the most important role in foreign policy is the United States Department of State, also known as the State Department, which is led by the Secretary of State. The U.S. Department is in charge of all international relations, which include representing the United States in the United Nations, leading diplomatic missions, negotiating treaties and agreements with other countries, and giving advice the President of the United States.