What Are Two Reasons That Scholars of Foreign Policy Generally

What are two reasons that scholars of foreign policy generally focus on the executive branch of the government?

A) The only legitimate foreign policy authority is the executive, and foreign policy requires a single voice.
B) Many agree that foreign policy requires a single voice abroad, and the executive holds all the purse strings.
C) Many constitutions specify that the executive, as the head of government, should be responsible for all policy making and the executive holds all of the purse strings.
D) Many constitutions specify that the executive, as the head of government, should be responsible for all policy making, and many agree that a country needs to have a single voice abroad.