"Macavity: The Mystery Cat" by T.S. Elliot was printed in a collection of poems written between 1909 and 1962, and prior to his death in 1965.
The poem is particularly humorous. The rhyme scheme provides a lilting quality that is upbeat and musical. There are wonderful descriptions, and the poem has been alluded to, even on Broadway in Frank Lloyd Wright's musical, Cats.
Of the choices given, "somber" means serious, and the poem is anything but serious. There is no indication that I can find to indicate an emotional response on the author's part. He is having too much fun with describing this thieving "cat." Macavity, Macavity, there's no one like Macavity..." is repeated.
The definition of "hip" is "fashionable" or "trendy." My first instinct would not be to select this word. Although this kind of writing might have been growing in popularity during Elliot's career, there is nothing to indicate this in the poem as it is written.
So unless you have been given other specific information in class, I would go with "excited," for one simple reason. The line "Macavity's not there" is repeated at least five times; in the version I read, the last (and sixth) time the author uses it, he has changed it to "Macavity wasn't there:" it is written totally in capital letters, finished off with an exclamation point. The poem has been "gaining momentum" till now—the exclamatory phrase insists that the cat is nowhere near the scene of the crime—and has, once again, outsmarted everyone! In the most basic terms, the way the phrase is printed and punctuated could convey excitement.