Answer: A) The words Blithe and Strong.
Explanation: The tone of a text or sentence is the author's or speaker's attitude towards the audience, the subject or even the characters of the text. There are many different kinds of tones, like: positive, negative, objective, sad, angry, etc. From the given options, the one that represent the language that contributes to the enthusiastic tone in the lines from "I hear America Singing" is option A: The words Blithe and Strong.