Question

how does the rhythm of iambic pentameter contribute to the meaning of \sonnet 130\?
the unbalanced rhythm emphasizes the subjects lack of beauty.
the stressed syllables highlight the speakers dislike for the subject.
the consistent rhythm softens the speakers unkind words about the subject.
the up - and - down rhythm adds to the comical descriptions about the subject

Explanation:

Iambic pentameter has a regular rhythm (unstressed - stressed syllable pattern repeated five times per line). In "Sonnet 130", the speaker describes his mistress in an unflattering way (e.g., "My mistress' eyes are nothing like the sun"). The consistent iambic pentameter rhythm provides a smooth flow. This rhythm contrasts with the harsh descriptions. It softens the blow of the unkind words. For example, if the poem had a jagged or irregular rhythm, the negative descriptions might seem more abrupt and cruel. The regularity of iambic pentameter makes the poem more palatable and perhaps even shows that despite the "insults", there is an underlying structure (and maybe affection, as the sonnet ends by affirming love).

Answer:

The consistent rhythm softens the speaker’s unkind words about the subject.