Answer:
When you are exercising, your muscles need extra oxygen some three times as much as resting muscles.
This need means that your heart starts pumping faster, which makes for a quicker pulse. Meanwhile, your lungs are also taking in more air, hence the harder breathing
The answer is D. The presence of oncogenes
Oncogenes is a gene that has potential to cause Cancer. Once it appear on tumor cells, Oncogenes often mutated at a very high level. When the cells critical function altered, they usually undergo a rapid cell death. But once oncogenes activated, those malfunction cells will not undergo rapid cell death, filling our body with malfunctioning cells
Melatonin is responsible for sleep and wake pattern known as the circadian rhythm.
