The main source of conflict at the Constitutional Convention was in regards to federal v. state power.
Federalists v. Anti-Federalists fought for weeks through published essays to push forward their view on whether their should be a strong Federal government or whether there should be a weak federal government to allow for strong and sovereign states.
The answer would be a. Bananas
The correct answer is the Seven Years War/French and Indian War.
From 1754-1762, England was in the midst of the Seven Years War. One piece of that conflict was the French and Indian War in North America.
The war was costly for England to fight on behalf of its colonists, who were being pugnacious and stealing land from the Indians and ignoring treaties.
As a result of the cost of the war that England fought on behalf of its ungrateful colonists, England taxed the colonies.
And people were not happy.