Answer: C) Noun Clause.
Explanation: an adjective clause modifies a noun or a pronoun and it is introduced by the words who, whose, whom, which, that, when or where. And adverb clause modifies a verb, and adjective or another adverb, and it is introduced by words like: after, although, as, as if, before, because, if, since, so that, than, though, unless, until, when, etc. A noun clause has the same function as a noun or a pronoun, it can be the subject of the sentence, the direct object, indirect object, etc. We can identify the noun clause by replacing it by the pronoun "it" or the pronouns "he" or "she." In this case, the bolded words are a noun clause because it is the subject of the sentence and we can replace it by "it": It surprised us all.
