Answer:
The sentence that is irrelevant to the theme of the first paragraph is "Ralph Emerson was also a popular American poet in the nineteenth century."
Step-by-step explanation:
The first paragraph is focused on giving information about the life and work of Emily Dickinson, and even when Ralph Emerson has some things in common with her like their nationality and the period, his information does not have any importance in relation to a thorough portrait of Dickinson's background and art.