Which literary technique does the poet use in these lines from beowulf?
that [sword] was not useless to the warrior now.

-caesura
-alliteration
-litotes
-kennings

The answer is "litotes"

Litote is a figure of speech, more precisely a figure of thought. It is used to slow down an expression by denying the opposite. It allows us to affirm something through negation. In Litote, the idea that the author wishes to pass is indicated by the denial of the opposite, this causes the speaker to attenuate an idea that could be aggressive, makes certain delicate situations more pleasant.

In this case, the phrase "That [sword] was not useless to the warrior now." either attenuates the idea that the sword was useful to the warrior.

i   believe   the   answer   is   d

"it's more of an essay than story, but perhaps it is best described as a mood-piece: it uses a lot of musical imagery, not to mention sea imagery, religious imagery, and any other imagery that suits his purpose."