Is part of the subject or predicate underlined in sentence was Herbert cleaning his messy room?

The underlined part of the sentence "Was Herbert cleaning his messy room?" is the predicate.

Here's why:

* Subject: The subject is the person or thing performing the action. In this sentence, the subject is "Herbert".

* Predicate: The predicate tells us what the subject is doing or being. In this sentence, the predicate is "was cleaning his messy room".

Let me know if you have any more questions!