I was very confused about this question. I tried to represent the passage in a conditional form and I had:
Kay disagree with each of the other candidates on more than one issue --> It is acceptable for her to vote for a candidate whose opinion differs from hers on at least one issue.
Otherwise --> It is unacceptable for her to vote for that candidate.
I chose C), because I thought the case we are given involving Legrand, Medina and Norton fell under "otherwise" category since the first conditional statement is telling us what Kay should do when there are candidates who disagree with her on at least one issue, but clearly Kay agrees with Medina on all the important issues of which there is only one.
Clearly, i am missing something or I misinterpreted the statements. It would be helpful if you could clear this confusion for me. Thank you.