What is the legal significance of the distinction between rule of reason violations and per se violations under the Sherman Act?

What is the legal significance of the distinction between rule of reason violations and per seviolations under the Sherman Act? 

Question 10 options:

Rule of reason violations require an agreement with at least one other party, but per seviolations can occur without an agreement with others. 

Rule of reason violations might be proven to be acceptable, but per se violations cannot be acceptable under any circumstances. 

Rule of reason violations relate to horizontal situations, and per se violations relate to vertical situations. 

Rule of reason violations must be proven beyond a reasonable doubt and per se violations must be proven with a preponderance of the evidence.