What is the meaning of the term theorem

There are 4 terms in the world of *Mathematical proof*
Lemma, Proposition, Corollary and Theorem.
There is no difference between a lemma,
proposition, theorem, or corollary - they are all claims waiting to be proved. However, we use these terms to suggest different levels of importance and difficulty. A lemma is an easily proved claim which is helpful for proving other propositions and theorems, but is usually not particularly interesting in
its own right. A proposition is a statement which is interesting in its own right, while a theorem is a more important statement than a proposition which says something definitive on the subject, and often takes more effort to prove than a proposition or lemma. A corollary is a quick consequence of a proposition or theorem that was proven recently

The correct answer is d, hope this