Answer :

The three main beliefs that guided American foreign policy by the turn-of-the-century were: 1. Americans believed that the growth of the U.S. economy depended on exports. 2. they felt the United States had a right to intervene abroad to keep foreign markets open. 3. They feared the close of an area to American products, citizens, or ideas threatened U.S. survival.
Answer; 
The three main beliefs that guided American foreign-policy;
 -Americans believed that the growth of the U.S. economy depended on exports.
-They felt the United States had a right to intervene abroad to keep foreign markets open.
-They feared the close of an area to American products, citizens, or ideas threatened U.S. survival.

Explanations;
The Foreign policy determines how America conducts relations with other nations of the world.
The policy is designed to further certain objectives and seeks to assure America's security and defense.
Additionally, it seeks the power to protect and project America's national interests around the world, which shapes the foreign policy and covers a wide range of political, economic, ideological, military and humanitarian concerns.