The answers are
subject and predicate. A sentence should have these two. If not, it won’t be a
sentence. It could end up as a sentence fragment. A subject is always a noun,
and it doesn’t have to have an adjective phrase for it to be considered as a sentence.
The two essential parts of a sentence are always a subject and a predicate. It
can be simple subject or compound subject, and simple predicate or compound
predicate.
