What is the simple predicate in sentence members of law enforcement quickly learned how to spot suspicious behavior?

The simple predicate in the sentence "Members of law enforcement quickly learned how to spot suspicious behavior" is learned.

Here's why:

* Predicate: The predicate is the part of the sentence that tells us what the subject does or is.

* Simple Predicate: The simple predicate is the verb or verb phrase that forms the core of the predicate.

* Subject: The subject of the sentence is "Members of law enforcement".

* Verb: The verb "learned" tells us what the subject did.

Let me know if you'd like more examples!