Final answer:
Sentences c and d contain restrictive clauses which are essential to the meaning of the sentences and help to define the subjects more narrowly regarding romantic poets and William Wordsworth, respectively.
Step-by-step explanation:
In identifying sentences with a restrictive clause, we are looking for clauses that are essential to the meaning of the sentence and are not set off by commas. A restrictive clause will narrow down the subject in some way. Based on this understanding, the two sentences that contain a restrictive clause are:
- c) "The poets who embraced Romantic ideals often rejected the constraints of neoclassical conventions."
- d) "One of the key figures, William Wordsworth, wrote extensively about the beauty of the natural world."
Both sentences use a clause that defines the subject more narrowly; 'who embraced Romantic ideals' specifies which poets are being discussed, and 'One of the key figures' indicates a specific person, William Wordsworth, in the context of the Romantic Era.