Final answer:
The correct answer is option a) Copperheads; they opposed the war and criticized Lincoln's policies.
Step-by-step explanation:
The opponents of the war in the North who troubled President Abraham Lincoln were known as the Copperheads, also referred to as "Peace" Democrats. Their opposition centered around Lincoln's policies on the civil war and emancipation, advocating for a peaceful reconciliation with the Confederacy rather than pursuing the war further.
They were members primarily from the southern Midwest and immigrant Catholics of northern cities, with notable leaders like Ohio Representative Clement Vallandigham. Despite favoring the Union, they demanded immediate peace and critically challenged Lincoln's exercise of presidential powers, leaving a substantial mark on the political landscape of the era.