D.) Diction refers to the choice of words with specific meaning , or connotations that helps the author to communicate his or her tone
He is using Parallelism, don't let the quiz fool you.
The literary device used on the title of the poem "War is Kind" is the following:
A. Irony
Irony is the expression of one's meaning by using language that normally signifies the opposite, typically for humorous or emphatic effect. This idea of expressing the opposite of what is actually being said/wrote is present on the title: in this case, by the use of the word "Kind".