He was young. is this a noun clause, an adjective clause, or an adverb clause?

M read the sentence.what best describes the underlined part of the sentence,and why? alma plans to visit london and paris, where her parentswent on their first trip together as a married couple.it is a restrictive relative clause because it begins with arelative pronoun, has both a subject and a verb, and is notnecessary to the meaning of the sentence.it is a nonrestrictive relative clause because it begins witha relative pronoun, has both a subject and a verb, and isnecessary to the meaning of the sentence.it is a restrictive relative clause because it begins with arelative pronoun, has both a subject and a verb, and isnecessary to the meaning of the sentence.it is a nonrestrictive relative clause because it begins witha relative pronoun, has both a subject and a verb, and isnot necessary to the meaning of the sentence.