1.What did many Anti-federalist conclude after they studied ancient Greek and Roman republics?

The correct answer to this open question is the following.

Many Anti-federalists concluded that the United States needed a free republic as a model for the new government after they studied ancient Greek and Roman republics.

Antifederalists did not agree on the idea of having a strong central government as the Federalists proposed. Antifederalists argued that a strong federal government could turn into tyranny, as was the case of the English monarchy. So during the Constitutional Convention in the city of Philadelphia, Pennsylvania, Federalists led by Alexander Hamilton and Jhon Jay, debated and argued with Antifederalists who supported a simpler form of government that included rights for their citizens, influenced by the ancient Greek form of Democracy or the Roman Republic.

your answer is

to dominate europe

and i know for a fact it can't be the others