A lot of mathematical statements come as consequences of a definition, as well as from applying theorems.
On the other hand, the word "given" is also used to anounce a condition that is satisfied and will be used for proving a statement.
The word "prove" is used to indicate that the person reading the text should make a proof by itself. So, it would hardly be used correctly as part of a proof.
Therefore, the correct answer is option C.
