Commas are required around an adjective clause only when the information it contains is NOT essential to the meaning of a sentence. Hope this helps!
Answer: B
Honestly I would look this one up one google
Do you have more information to go with this?
I believe the correct answer from the choices listed above is option B. The correct sentence would be "If she doesn't graduate in December, she willgraduate in June." This is the only sentence where the comma is in the right place while the others are wrongly placed.