Answer:
D. It emphasizes the dangers of traveling by land.
Explanation:
In paragraph 11 of Five Weeks in A Balloon by Jules Verne, we can see that the narrator is telling us of all the dangers that could have happened if they decided to walk instead of fly in a balloon, like: their beasts would have died, they would have been very tired, the humidity would drive them crazy, wild beasts and native tribes might have attacked them, etc.
In paragraph 13, he is just emphasizing these dangers further by talking about terrible stories that other brave travelers told, those who decided to walk rather than fly.
