How does regular exercise help make us more alert and energetic?
A.
It gets our hearts beating faster and gives us a rush of energy.
B.
Exercise increases our endurance and therefore we feel less tired.
C.
During exercise the brain releases endorphins, the chemicals that help improve our mood.
D.
We breathe in more oxygen while exercising, which helps us feel more awake.

C. During exercise the brain releases endorphins, the chemicals that help improve our mood.

Explanation:

Regular exercise benefits us to be more alert and active by delivering a substance that enhances the overall mood of a person. This substance is called "endorphin". Also, it improves blood flow and stimulates the heart. More oxygen would be in your brain and blood supporting you to be more alert and vigilant.Regular physical activity can develop your muscle power and boost your stamina. Exercise transports oxygen and nutrients to your tissues and helps your cardiovascular system functioning more efficiently. And when your heart and lung health advances, you have more energy to tackle daily tasks.