<span>Controlled variable is a variable that was made constant in the research. That was because the controlled variables can influence the dependent or independent variable. If the variables is not made constant, it can alter the research result and made it invalid.
In this case, </span>the caffeine and alcohol intake might alter the physical activity or the blood glucose so it should be controlled.
the answer you are looking for is B. Glucose is broken down into two pyruvate molecules.
this process occurs during glycolysis
It couldn't be analysed chemically because it's chemical composition is to complex. It would be hard for us to analyse them because once it has been removed from the organism, it ends as protoplasm only.