Answer:
The correct answers are -
Definition, Postulate, Corollary and Theorem.
Step-by-step explanation:
When we want to prove something, we already know that one thing is already there, proven and we have to prove the other part.
A definition is something that is absolutely true and valid. It can also be used to prove another statement.
A postulate is a statement that is assumed to be true, and is used to prove other statements.
A corollary is a direct consequence of an already proven fact, and can also be used used to prove other statements.
Theorems are already proven statements. These are used to prove other statements as well.
