Final answer:
Among the provided options, the word 'baby' contributes most to the informal tone of the poem. It is often used in conversational or colloquial English, making it less common in formal texts, thus contributing to the informal tone.
Step-by-step explanation:
In the context of any literature, the tone is the author's attitude towards the subject or audience. Words such as 'gonna' and 'baby' are commonly associated with an informal or casual tone. Among the provided options, the word 'baby' contributes most to the informal tone of the poem. It is often used in conversational or colloquial English, and is less likely to be found in formal or academic texts. This gives it a friendly, personal, or informal attribute, thereby contributing to an informal tone in the poem.
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