Explanation
Correct answer: A.
Choice A is the best answer because the text indicates that Fox-Foot doesn’t let the group build a fire or create a canoe landing when it’s time for supper. This context suggests that he doesn’t want anyone who might be following the group to see any sign of them or their activities. In other words, Fox-Foot doesn’t want there to be any trace, or evidence, of the group’s movements ("their passing") through the area.
Why the other choices are wrong
Choice B
Choice B is incorrect because the text conveys that Fox-Foot doesn’t want the group to be detected, not that he doesn’t want their presence to create a blemish, or a spoiling flaw, in the area; human activity could disturb a natural environment, but the context emphasizes that Fox-Foot is instead focused on avoiding giving any sign of the group’s movements through a place ("their passing") to anyone who might be following them.
Choice C
Choice C is incorrect because the text focuses on Fox-Foot’s desire to avoid detection by those who might be following the group. This context conveys that Fox-Foot doesn’t want to create any signs or evidence of the group moving through a place ("their passing"), not that he doesn’t want to leave behind some quantity of their presence; indeed, it isn’t clear what an amount of a group’s movement would be.
Choice D
Choice D is incorrect because nothing in the text suggests that the group has a sketch, or rough drawing, of their movements through that area ("their passing") that might be left behind. Rather, the context emphasizes that Fox-Foot is focused on ensuring that the group doesn’t give any kind of indication of their presence, as he wants to avoid detection by anyone who might be following the group.