In which of these systems can parts of the oxygen cycle be found?

a. atmosphere
b. biosphere
c. geosphere
d. hydrosphere

The oxygen cycle can be found in all but the geosphere. There's oxygen in the atmosphere, so it has to be there, and the biosphere includes living things, which breathe oxygen, and water (hydrosphere) is made up of partly hydrogen, so there has to be oxygen there as well.

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.

if you add everything up correctly you should get 69 i got this because 50 plus 19 is it