When we breathe, our respiratory system takes up oxygen and carbon dioxide or other useless gases go out . The oxygen combines with the haemoglobin in the blood of the circulatory system . This is transferred to all the cells of our body to get energy.
Answer: for me the best option is D.
Explanation: lets explain this.
Cellular respiration begins with a process that divides the glucose within the cells making it readily available as a source of energy. This process can occur without oxygen (anaerobic respiration) or in the presence of oxygen (aerobic respiration). Anaerobic respiration generates more excess waste (lactate) than aerobic . Besides, high levels of lactate build within the muscle cells. Excess lactate slows the cellular respiratory process and is experienced as a burning sensation in the muscles if exercise continues.
