A few pages before this excerpt, Momaday mentions deep silence when nothing moves and it doesn't have any sound. Then, again he mentions this silence which is given in this excerpt. The meaning is not an allusion, it has got a direct meaning. The correct answer is the last option.
Get on subject, Be yourself, eye contact, don't hide behind the lectorn, posture, comppelling words and phrases, vary cadence, talk about intresting subjects, purpose, be on task.