Explain the roles of congress and the president in foreign policy. (site 1

The Secretary of State is the head of the United States Department of State. He is responsible for representing American diplomacy; currently, Mike Pompeo is in the position.  

The constitution in principle establishes the predominant role in foreign policy for Congress (Article 1 Section 8 of the Constitution of the United States). However, the powers of the president have been reaffirmed on numerous occasions by the Supreme Court, which as early as the 1930s admitted the validity of sole executive agreements, that is, agreements signed by the president alone with foreign power, unlike treaties that require the approval of the Senate.  

In addition to the general powers of the Congress which also apply to foreign policy, it has several foreign policy powers: to regulate foreign trade; to define and punish crimes committed on the high seas; to ensure a common defense; to raise and maintain the armies; and to declare war. Pursuant to the check and balance mechanism governing the separation of powers in the United States, the Senate must ratify treaties by a two-thirds majority and confirm appointments by simple majority.  

according to classical republican political theory, which democratic republics would function best?

a.   small republics, with people who had similar interests

b.   large republics, with people who had competing interests

c.   republics made up entirely of landowners

d.   republics made up entirely of servants

the density would be a smaller number.