B) the state department
The Administrative Branch and the Congress have legal duties for U.S. foreign policy. Within the Executive Branch, the State department is the leading U.S. international affairs agency, and the Secretary of State is the President's chief international policy consultant.
The State Department proposes U.S. intentions and concerns in developing a freer, more stable, and the wealthy country through its fundamental role in promoting and executing the President's international policy.
The State Department also encourages the foreign affairs actions of other U.S. Government entities including the U.S. Agency for International Development. It also presents a host of significant assistance to U.S. residents and to immigrants attempting to visit or migrate to the U.S.