He original party system in the united states pitted the federalists, supported by against the jeffersonian republicans, supported by a. agrarian interest; merchants b. merchants; loyalists c. loyalist; agrarian interests d. merchants; agrarian interests

I found the answer on the internet. The question starts with "The" and not "He".
The original party system in the United States pitted the federalists, supported by MERCHANTS, against the Jeffersonian republican, supported by AGRARIAN INTERESTS.

Federalists were the supporters of the proposed Constitution of the United States. The Agrarian interests mean the agricultural interests that consisted of Agrarian Society.

(d.) MERCHANTS, AGRARIAN INTERESTS