Answer:
The words that creates a lofty, or intellectually superior, tone is cultivate.
Explanation:
"Cultivate" is not commonly used in English in its original meaning, which would be the action of preparing and using the soil for gardening and growing crops. When "cultivate" is used, it is usually in more intellectual, formal texts, with the meaning of pursuing, acquiring, or developing a certain characteristic. That is the case in this excerpt by Mark Twain. The tone becomes more lofty, superior, by the use of this cultured word. He could very well have said, "one faculty which a pilot must incessantly work hard at", or "one faculty which a pilot must incessantly pursue", but he chose "cultivate" for the lofty tone it conveys.
