When We Put a Declarative English Sentence into Standard Form

When we put a declarative English sentence into standard form as a categorical proposition, what happens to the main verb if it is not a form of the verb "to be"?

A) It always becomes the copula.
B) It is removed and replaced with a form of the verb "to be."
C) It is always absorbed into the subject class.
D) It is always absorbed into the predicate class.
E) Sometimes it is absorbed into the subject class, and sometimes into the predicate class.