Final answer:
In stanza 2 of 'Dulce et Decorum Est,' the speaker uses metaphor.
Step-by-step explanation:
In stanza 2 of 'Dulce et Decorum Est,' the speaker says 'under a green sea, I saw him drowning.' The figurative language being used here is metaphor. A metaphor is a figure of speech that makes a comparison between two unlike things without using 'like' or 'as'. In this case, the speaker is comparing the battlefield to a green sea and the soldier drowning in it.
Learn more about figurative language in 'Dulce et Decorum Est'