The correct answer is C. before the conjunction.
If there is a conjunction between two independent clauses, then the comma will be placed in front of it. For example: <em>We had a lot of fun at the beach, but I feel tired now. </em>
As you can see, the comma is located in front of the conjunction <em>but. </em>Simply placing a comma between the sentences (without a conjunction) creates a run-on sentence, and that is grammatically incorrect.
Answer:
I answered this already, i said it was answer B.
<span>Being active for 30 minutes a day strengthens your heart and lungs.
This actively supports the idea of how exercise helps maintain good health.</span>
