Tom and Phyllis said they would pay our dog's boarding costs.

What is the subordinate clause?
Is it our dog's boarding costs

A clause must have a subject and verb.

Please try again.

Yes, "our dog's boarding costs" is the subordinate clause in the sentence "Tom and Phyllis said they would pay our dog's boarding costs." A subordinate clause is a group of words that contains a subject and a verb but cannot stand alone as a complete sentence.

Yes, "our dog's boarding costs" is the subordinate clause in the given sentence.