Teachers always want to say more; when a student asks a question, the mind of the teacher fills with ideas of ways to impart the information--explanations, diagrams, pairs of contrast and similarities, quiz questions, challenge questions, and the like. But no teacher I know ever has time to exhaust even a single idea. There are always just too many different questions to answer and too many doubts that could arise. That said, I thought I might keep a list of the topics I wish to expand ...