The speaker's mood in this excerpt is playful. The right option is the second one.
Explanation:
These lines from Robert Frost's poem "Mending Wall," presents a harsh truth playfully and subtly. The poem is an insight into those uncertain times when two rural neighbours on a spring day meet and walk along the wall which separates their properties. They also repair it when needed. Usually, the mending wall symbolizes the separation between the two neighbours which subtly presents the theme of the poem. It points out the self-imposed barriers which stop or prevent human interaction. We see that the speaker's neighbour keeps rebuilding a wall without any reason. The wall doesn't even benefit anyone and the fence is harmful to their land on the other hand but still, the neighbour keeps maintaining it relentlessly. In these lines, this theme or thought of the poet is expressed in a playful tone.