I think is D,,,,,,,,,,,,,,,,,
How does changing the type of exercise effect heart rate in bpm?
Or
How does changing the amount of reps of [insert exercise here] affect heart rate in bpm?
You have to first make some observations and then ask a question. Then you make a hypothesis (or guess) what the answer is - do the experiment to see if you're right!
Answer: Your answer is indeed <u>A. Fair treatment.</u>
Hope this helps!