Answer: B) Noun clause.
Explanation: A noun clause is a group of words that acts like a noun (it is the subject or object of the sentence). A noun clause usually starts with the words; who, what, why, when, where, how, that, whoever, whether and that. In the given sentence, the bolded words are an example of a noun clause (it acts as the subject of the sentence). So the correct answer is the corresponding to option B.
