Take, for instance, the description of "an American" friend who has provided the speaker with information about preparing humans for consumption. This gives us a general idea, though within a comical context, of the reputation "Americans" still had in the early eighteenth century for being uncivilized, veritable "savages." But it's hyperbolic. (Hopefully Swift knew that Americans were not really like this, even at that time.)
Visual (sight) because of the descriptive comparison of the outlines, you can almost see what they look like. It is like the author hands you a photo of the words in action.
The answer is: [D]: "will have" . _____________________________________________________ "On Friday Vanessa <u> will have </u>been travelling for a month." ______________________________________________________