It's to show an exception (which is often the purpose of "yet") because in the first clause it identifies an action, then then it's like "but wait, maybe the action didn't really get going" in the second half of the sentence
Social learning theory is a type of process when learning. This occurs in a social setting. It can happen just by observing or direct instruction.
Moral is the lesson you learn from the story
They talk about the subject on the end of the day
I believe that the correct answer is C because that literally shows it, but it also could be A because that is a more accurate detail that she actually missed it, and that it wasn't just a random bus. But, I think it is most likely A because C is just imagery. Hope this clarified it a little bit!