<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.
This is cyclic change because the population is consistently going up and back down.
D is probably right cos you are comparing data
A study created to make genetically modified orginisms.
The Answer is C. stratosphere
