Answer:
B). 'Where complaints are handled'
Step-by-step explanation:
Adjective clauses are illustrated as the subordinate or dependent clause beginning with a relative pronoun or relative adverb and include a subject along with a verb. Such clauses function as a modifier in the sentence and require a principal or dependent clause to complete the thought.
As per the question, the adjective clause in the given sentence would be characterized as 'Where complaints are handled' as it begins with the relative pronoun and carries a subject(complaints) and a verb(handled). It is functioning as an adjective in the sentence to modify the noun 'department'. Since it justifies the above claim thus, option B would be the correct answer displaying an adjective clause.