Answer:
Number 1 and 4 are your best options. Although I am unsure of the answer, i hope this helped you narrow them down! good luck!
hello the answer is B. intensity It reflects how difficult an exercise is for a certain person to complete and the amount of oxygen the body uses to do an exercise and the amount of calories burned while doing the activity. The higher the intensity, the harder the activity, the higher the heart rate, and the more burned calories hope this helps!!!
kidneys remove the waste.
The answer is A, the immune system