What is the predicate adjective in sentence Swimmers should be careful of sharks?

The predicate adjective in the sentence "Swimmers should be careful of sharks" is careful.

Here's why:

* Predicate: The predicate is the part of the sentence that tells us something about the subject. In this case, the predicate is "should be careful of sharks."

* Adjective: An adjective describes a noun or pronoun. "Careful" is an adjective describing the subject "Swimmers."

* Predicate Adjective: A predicate adjective is an adjective that follows a linking verb (like "be") and describes the subject.

Let me know if you have any other questions!