Still not clear on predicates for my son.
The sentence He traveled by train and riverboat.
Is traveled by the simple predicate?
The predicate in any sentence is the main verb and all the words and phrases that go with it. Or you could say it consists of everything in the sentence that isn't part of the complete subject!
In your sentence above -- yes, the simple predicate (main verb) is "traveled" and the complete predicate is "traveled by train and riverboat."
=)