What is the purpose of this conversation()

单项选择题During heavy exercise, electrolytes are lost in sweat. These electrolytes must be () to keep the electrolyte concentrations of the body fluids constant.

A. retained
B. reduced
C. returned
D. replaced

单项选择题Coconut water is a natural isotonic beverage, with the same level of () as we have in our blood.

A. medical saline
B. electrolyte balance
C. blood plasma
D. intravenous fluid