Heart rate, color, irritability, muscle tone, and breathing
Answer:
The correct answer is -
the independent variable - if fertilizer added or not,
the dependant variable - the height of the plant and
the standardized variable - 200ml water
Explanation:
In this study, the student wanted to see the effect of the fertilizer on the growth of the plant so the independent variable is the treatment of the fertilizer as manipulated or the independent variable is the factor which is affected or changed purposely during an experiment while other variables remain constant.
The dependent variable is the factor that is based or depends on the independent variable and measured to see the effect which is the height of the plants in this case.
The standardized or the control variable is the variable that remains constant throughout the experiment, 200 ml water treatment is the control variable in this experiment.
The answer to the question is c) a dendrochronologist interprets tree rings
