One cannot be a teacher without being a student just as one cannot be a father or mother without being a son or daughter. A teacher is a student throughout his career.
During student life one thinks that they will be relieved of learning, at least from books, after their student life is over. But it never happens. Learning becomes a life long process. Though when one grows up he starts learning less from books and more from life.
Life is the biggest book and two books (lives) cannot be similar. We can read books that belong to others but we cannot read and understand the book of life that is not ours. The more we try to read our own book (life) the more comfortable we are with ourselves and others around us. It will invite misery for us if try to read books (lives) of others.
The only difference between a teacher and a student is that a teacher starts accumulating and sharing knowledge at a certain stage and whereas a student remains a student so long as he just accumulating knowledge and has not started sharing it.
The reason why a teacher has answer to all the question from a certain chapter is that he has studied the chapter several times before teaching it to his students. Besides, it is their life full of rich experiences that helps them to relate topics. It makes topic interesting and easy too.
Likewise the students too will have all the answer if they revise topics several times and try to relate them to their life and surroundings.