What type of clause is shown in parentheses? carla had left a message on the answering machine about (whomever you had spoken to)?

We are given the sentence above and is asked for the type of clause. The clause whomever you had spoken to is dependent since the sentence (original) cannot complete a thought without the clause in this parenthesis. If the sentence otherwise could stand on its own without the clause, then the clause could have been independent. 

Ithink this question is true