Justin designed an experiment to find out how running up bleachers affects his heart rate. first he records his resting heart rate and then turns up the bleachers 10 times. each time he reaches the top, he records his heartrate then rests 20 minutes. which is involved in justins experiment?
A. replication
B. repetition
C. both repetition and replication
D. neither repetition nor replication

In Justin's experiment to find out how climbing stairs affects his heart rate, by doing it 10 times, he involves an experimental study of repetition (option B).

Explanation:

In experimental design, repetition involves performing an experiment several times, maintaining the same experimental conditions,In Justin's experiment, each repetition is done by walking up the steps and taking 20 minute rest intervals.

In the replication the experiments are repeated, but varying the experimental conditions at random and recording the results. This could happen if Justin varied the distance traveled at each opportunity or carried objects of different weight.