8. What is the effect of the author's use of the word "must" four times in the sentences at the beginning of paragraph 5?
a. It emphasizes that the ideas in these sentences are critical for the race.
b. It demonstrates that the ideas in these sentences reflect what the musher believes.
c. It indicates that the ideas in these sentences are essentially the same.
d. It shows that the ideas in these sentences are the only important traits.