let me try to answer your 1st and 2nd question, and leaving the 3rd one for those who are familiar with the exam to answer
1st, the reason that it should be A is because the word "divided" is actually an adjective meaning they have different opinion. So, divide on should be the answer. The B, by, when adds into the senstance, it would mean the owners were separated by......... which obviously is not what the senstace is supposed to mean
2nd, the answer should be A, but i am not confident about it.
i would also love to hear what other thing about my answer to your inquiries
Student or Learner