C, the heart. The heart is a super muscle that is controlled involuntarily by the brain and beats at a medium rate. with each beat the heart pulls blood in and out of arteries, which then rushes through the arteries and into veins. The veins the pass the blood cells containing oxygen past muscles containing cells that need the oxygen to function, and the cycle repeats.
Answer: B.
When a person is working hard through cardiorespiratory exercise and conditioning, his resting heart rate decreases because each beat sends a bigger burst of blood and fewer beats of the heart is needed.
Moreover, it is recommended that after a chronic cardio training, the person must walk for a while to let the heart recover to have normal heart beat.
Over time, improved cardiovascular fitness improves resting and recovery heart rates.
A person's breathing rate can be affected biologically if they have shortness of breathe, asthma, in some cases anxiety.
Environmental would be weather, if it is very cold their breathing rate will not be the same with moderate temperature.
Internal factor would be lungs. If a person has smoked or has any sort of lung damage or disorder this will affect whether the person has a normal breathing rate
An infection is a disease caught by a person or people that could make someone or something sick. It can be cured or repelled with a special medication.
It is true that despite the relatively new nature of HIV/AIDS there are laws in place to protect those that are infected.