Even after the unification, that gradually happened between 1815-1871, the conflict still continued mainly because of quite major regional and ethnic differences. Since Italy was separated for quite a long time, different traditions, views on politics, and much more appeared within these societies. If you take a closer look at the image below, you will see how many different societies lived separately. You could only imagine how diverse that area was.
The best option from the list would be "<span>The guillotine was an effective instrument for instilling fear and conflict," since this is an opinion that needs to be supported with historical evidence. The other options are simply facts (or non-facts). </span>
The primary difference between Presidential and Congressional Reconstruction plans was that the presidential plan was far more progressive, while many in Congress wanted to punish the South.