Answer:
4. Nature, to suggest that walls aren't natural like the pine trees and stones are.
Explanation:
Personification is the giving of human characteristics to a non-human idea or abstract thought. In other words, making a nonliving thing appear lifelike or have human characters is known as personification.
In the poem "Mending Wall", Robert Frost used personification right from the start of the poem. The initial lines
"Something there is that doesn't love a wall
That sends the frozen-ground-swell under it,
And spills the upper boulders in the sun;
And makes gaps even two can pass abreast"
uses personification for 'nature' or natural forces like erosion. The speaker personifies the natural force or act of erosion, making it seem like it doesn't like the construction of the wall. This suggests that the walls are not natural.
Thus, the correct answer is option 4.
