Copperheads were:
a. southerners who worked to sabotage the confederate cause
b. slaves who escaped to freedom and joined the union army
c. northern democrats suspected of having confederate sympathies
d. members of the confederate congress who wished to negotiate peace

Copperheads were people in the Union who did not like the American Civil War and wanted peace with the Confederates. Lets take a quick look at the options:

A. Southerners who worked to sabotage the Confederate cause  No, they were northerners.

B. Slaves who escaped to freedom and joined the Union army  No, this took place in the government and did not have anything to do with the army.

C. Northern Democrats suspected of having Confederate sympathies

Yes! This is the best option.

D. Members of the Confederate Congress who wished to negotiate peace No, they were Union Democrats that wanted to negotiate peace.

C. Is the best option, Northern Democrats suspected of having Confederate sympathies .

I hope this helps! :)

the answer is c my brotha. c.   formed an alliance with the soviet union.

big fat oof x