What unresolved question was answered by the last two sentences of The View From Saturday?

The unresolved question that is answered by the last two sentences of the novel is one that has dogged Mrs. Olinski throughout the course of the narrative, the question being, how did she pick her team?  Mrs. Olinski has been asked that question countless times, by coworkers, administrators, faculty of other schools, and the media.  Mrs. Olinski realizes that she does not know the answer to the question, and struggles to analyze the situation throughout the story.

Mrs. Olinski picked Noah to be on her academic team first, followed closely by Nadia and Ethan.  She had considered asking Hamilton Knapp to be the fourth member, but something kept telling her that he would not be a good choice.  Ham was smart, but he was also naughty, but naughtiness in itself should not have eliminated him from consideration in Mrs. Olinski's mind, because "bad boys had always held a certain charm for her".  Still, something kept  Mrs. Olinski from choosing him.

Mrs. Olinski did not consider Julian until she visited Sillington House and saw the four children, Noah, Nadia, Ethan, and Julian, interacting with each other with an unselfishness and mutual sympathy which was seldom found in sixth graders.  On that same day, she witnessed Hamilton Knapp's instigation of a really cruel stunt during the school play.  It was at this point that Mrs. Olinski knew that Julian should be the fourth member of the team.  Hamilton Knapp was a downright mean person, and Julian was just the opposite (Chapter 5).

Mrs. Olinski still isn't aware of exactly how she chose her academic team at the end of the story; at times she feels that she did not choose them at all, but that rather, they chose her.  She asks the Souls directly in the last paragraph of the book, "Did I choose you, or did you choose me?"  The Souls' answer, a resounding "Yes!", affirms that the answer is somewhere in the middle - Mrs. Olinski, as their teacher, did choose the Souls on the basis of their character, and the Souls, in deciding to work together to kindly give their teacher "a lift" when she needed it, chose her as well (Chapter 12).