Why do we use topographical maps ? what does every map / hill on a topographical map start at & how do you know ?

Thayer sometimes finds it difficult to understand what his instructor is saying. he raises his hand in class and asks his instructor to elaborate on what was just said, but it rarely . what should thayer do to overcome this obstacle? a. during class, ask other students what the instructor means b. raise more questions in class c. join a study group of his peers d. try to do the best he can with the information he has