2. an adverbial clause modifying the verb are keeping
Explanation:
Adverbial clauses usually begin with a subordinating conjunction like <em>since, after </em>and <em>before</em>, and they contain a subject and a verb. Therefore, the sentence given is a complex sentence, consisting of a dependent or subordinate clause (<em>Since they already have an older cat</em>) and an independent one (<em>they are keeping the kitten in a separate room for a few days</em>).
