Ow does regular exercise make us more alert and energetic?

Well the hormone would be one thing. I'd say because it strengthens our heart muscles and trains our breathing pattern to be more effective. These would lead to more efficient transportation of blood and hence oxygen to our whole body including our brain. Our brain becomes more alert, and our body more energetic.

Ithink it’s d. that should be correct.

Answer(d) application of hot and cold packs;