Answer:
The independent Variable in the given scenario IS "the concentrations of the test substances used"
Step-by-step explanation:
The independent variable characterizes as the variable that can be changed or controlled in a logical trial. It define the cause or effect behind a result. Independent variables are the factors that the experimenter changes to test their dependent variable. An adjustment in the Independent variables legitimately causes an adjustment in the dependent variable. The impact on the dependent variable is estimated and recorded.