The immediate energy system (ATP-PC) relies on:

a. the reactions of glycolysis

b. oxygen availability in the immediate cellular environment

c. the high-energy phosphates stored in muscle cells

d. the oxidation of lactate

c. the high-energy phosphates stored in muscle cells

Explanation:

Phosphocreatine (PC) or creatine phosphate is a compound rich in energy. It has energy stored in it which can be used to phosphorylate ADP into ATP. The phosphocreatine is stored in muscle cells when muscles are not working. The produced ATP serves as an energy source for muscle contraction. The creatine produced during ATP production is phosphorylated again into PC using ATP when muscles are resting.