Final answer:
The main effect of the Embargo Act was to cause a significant decline in exports to Europe, leading to economic hardships in the U.S., and failing to stop the British and French harassment of American shipping.
4 is correct
Step-by-step explanation:
The main effect of the Embargo Act passed during Jefferson's presidency was a significant drop in exports to Europe, which led to widespread economic hardships in the United States. This was in stark contrast to its intended purpose, which was to put economic pressure on Great Britain and France to stop the harassment and forced impressment of American sailors and respect American neutrality.
The Act ultimately failed to deter British and French aggression and instead caused detrimental effects on American commerce, including a decline of business activity by 75 percent from 1808 to 1809, increased unemployment in seaport cities, and a rise in bankruptcies.