Final answer:
The efef rhyme scheme is a feature of the poet's style created by the sonnet form in William Shakespeare's 'Sonnet 18', adhering to the traditional Shakespearean sonnet structure.
Step-by-step explanation:
In Sonnet 18 by William Shakespeare, the sonnet form influences the poet's style by adhering to a specific rhyme scheme and structure. The correct answer to the question is 'd) The efef rhyme scheme'. This particular rhyme scheme is characteristic of the Shakespearean sonnet, which traditionally consists of three quatrains followed by a final couplet with the pattern: abab, cdcd, efef, gg. Shakespeare's sonnet emphasizes the eternal nature of the subject's beauty, defying both time and death, using this structured rhyme to create both a lyrical sound and a cohesive argument throughout the poem.