Identify the underlined clause:
I know where he lives.

The underlined clause in the sentence,"I know where he lives" is a:

Option 2: Noun clause.

Explanation:

In this sentence, "where he lives" serves as a noun clause. A noun clause functions as a noun within a sentence. It can act as the subject, the object, or the complement in a sentence. In this case, the clause "where he lives" is acting as the object of the verb "know." The clause is providing information about what is known, hence functioning similarly to a noun. Adjective clauses and adverbial clauses, on the other hand, modify nouns and verbs, respectively, and do not function as the main subject or object in a sentence.