What “mischief” does the speaker do?

The speaker’s “mischief” is that he wonders whether he can put a new idea in his neighbor’s head: that they may not need the wall. He points out that their trees won’t cross the boundary and eat each other’s fruit, so he questions the tradition of mending the wall. The answer is B, “He questions the tradition of wall-mending.”

AI-written and checked against the verified answer.