Which phrase from the poem adds to the idea that a mouse exercising on a piano is a silly thing?

this answer was editing it cause i couldn't delete!

the underline word is basically like a prepositional phrase.

the answer is:

when will (v) the books (n) be (v) due?

nouns refer to people (other than pronouns), places and things, whereas verbs describe actions and are usually part of the predicate of a sentence. finally, pronouns can work as nouns and identify the participants in speech.

in the example sentence, "will" is a verb part or auxiliary verb, "be" is an infinitive verb and "books" is a plural noun.