The correct answer is B. unrhymed poetry written in iambic pentameter.
Shakespeare often used blank verse in both his sonnets and his plays. It means that there is no rhyme at the end of each line, the way many poets write. Also, iambic pentameter is used, which means that there are ten syllables in each line (penta means 5, meter consists of two syllables), and the first syllable is always unstressed, followed by a stressed syllable (iamb).