Which noun is the subject of this sentence A can be a person place or thing?

The subject of the sentence "A can be a person, place, or thing" is "A".

Here's why:

* Subject: The subject is the noun or pronoun that performs the action of the verb.

* Verb: The verb in this sentence is "can be".

* "A" is performing the action of being a person, place, or thing.

Even though the sentence talks about people, places, and things, the core subject is the indefinite article "A".