The correct answer is, D. It will follow a general noun and is not set off by commas. A restrictive adjectival clause (also called essential clause) is essential to the meaning of sentence because it refers to specific noun in sentence. Deleting this clause will change the meaning of the sentence. Since these are essential, the are not set off by commas. E.g. All students who have scored more than 80 percent will move to next round.