Iambic pentameter is a metric parameter that defines rhythm and the emphasis of syllables in a line of a poem. Iambic is a beat with a combination of one unstressed syllable with one stressed syllable. While pentameter is a rhythm composition of five metrics. So Iambic pentameter has a line of five non-stressed-stressed syllables.
Shakespeare’s “Sonnet 100” has fourteen-line in Iambic pentameter which the emphasis contributes to highlight the important words and the rhythm intensifies the emotional impact, which are in these two options:
The stresses highlight important words and concepts.
The regular rhythm intensifies the emotional impact.
I hear in the chamber above me (a) the patter of little feet (b) the sound of a door that is opened (c) and voices soft and sweet (b) [it rhymes with "feet"]