​Bob, Kara, and Mark are partners in the BKM Partnership. Bob is a​ 40% partner and has a June 30 tax yearminus−end. Kara owns a​ 40% interest in the partnership and has a September 30 tax yearminus−​end, and Mark owns the remaining​ 20% interest and has an October 31 tax yearminus−end. The partnership does not have a natural business year. What is the required tax yearminus−end for the partnership​ (if no Sec. 444 election is​ made)? A. September 30 B. October 31 C. December 31 D. June 30