The correct option is Snake.

Explanation:
The quoted lines are taken from the final stanza of the famous poem Snake by D. H. Lawrence (David Herbert Lawrence), published in 1923 as part of his collection Birds, Beasts and Flowers.

In the poem, the speaker encounters a snake drinking at his water-trough on a hot day. Conflicted between his natural admiration for the beautiful, peaceful creature and the "voices" of his social education prompting him to kill it, he ultimately throws a clumsy log at the snake as it retreats into a hole. He immediately regrets this act of hostility towards a creature he perceived as kingly.

The lines:
“And so, I missed my chance with one of the lords
Of life.
And I have something to expiate:
A pettiness.”
reflect the speaker's deep sense of guilt and self-reproach. He feels he has acted in a petty, uncivilized manner toward "one of the lords of life" and needs to atone (expiate) for his behavior. Thus, these lines directly identify the poem as Snake.