Which line from the poem "Wave" best develops its tone?

Wave

My child (line 1)

Born to me by water (line 2)

And by water (line 3)

Swept away. (line 4)

The tone of a poem is the attitude you feel in it, the writer's attitude toward the subject or audience. In this case, this is a sad poem, so the line that best develops its tone would be Line 4, where specifically indicates the boy is no longer anymore.

The writer's attitude in this poem, towards the child is that it is now gone. He wants the audience to have a sense of loss with this situation; in fact, the whole poem projects a grim and sad atmosphere.

That combination of intentions, ideas and the overall attitute the writer lays in his creation is called tone.

Therefore, correct answer is D.) Swept away, since it implies something is lost.