I think it's B. Possibly.
<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>
To get across the point that he is a lesser than those he speaks to.
It shows the doer of the action.It comes before verb and indicates this action or work is done by it/him/her etc.Ex.Susan switched off the lights. Who switched off the lights? The answer is Susan (subject of the sentence)