Asap when you exercise, your muscles are hard at work! to allow your muscles to do all that work, they need more nutrients and oxygen delivered to them so they will have the energy they need. which body system supply them with those necessary things? a. digestive and respiratoryb. circulatory and respiratoryc. circulatory and excretoryd. respiratory and skeletal

The correct answer is option B, that is, circulatory and respiratory.  

When one exercise, the muscles move more energetically than when one is at rest. The rate of metabolism enhances, and the need for energy upsurges, thus, there is a need for the production of more of ATP, that is, the chemical energy molecule. For the production of ATP, there is a requirement of oxygen, so the more ATP one generates, the more oxygen is required by the body.  

In such a situation, the aerobic heartbeat upsurges, in order to circulate the oxygen to the muscles, and eradicate the toxins from the cell at a brisk rate. This elevates the blood pressure. Eventually, to get more oxygen into the bloodstream, and to eradicate the toxins, the rate of breathing upsurges, and the lungs contract and expands at a higher rate. Thus, both circulatory and respiratory system works in combination when one exercise.  

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