One way that opposition to civil War was suppressed was the denial of the right of_________

I think it is assembly, just trying to double check please.

What are your other choices?

There are no choices. The actual statement is One way that opposition to civil War was suppressed was the denial of the right of ex post facto.

and it is false.
so we have to find the right answer.

I can't find any indication that assembly is the correct answer.

Study your text carefully.

What about Habeas Corpus?

http://www.etymonline.com/cw/habeas.htm

Was the answer to this question ever determined?

You are correct! One way that opposition to the Civil War was suppressed was through the denial of the right of assembly. To confirm this, you can look at historical sources or references that discuss the period during the Civil War. These sources may include documentaries, books, scholarly articles, or primary documents from that time. By studying these sources, you can find information about the restrictions placed on civil liberties, including the denial of the right to assemble, as a means of suppressing opposition to the war.