Answer:
Secretary of State is the correct answer.
Step-by-step explanation:
According to US constitution the president decides the US foreign policy and the Secretary of State is his chief foreign affair's adviser. Secretary of State is appointed by the president with the consent and advice of the senate. He carries out the president's foreign policies through foreign service and state department. The duties of the secretary of state has not changed since the creation of Department of foreign affairs since 1789. He also conducts the negotiation related to US foreign affairs.