Which describes how the talk test is used to check exercise intensity?

I believe if you are so out of breath that you cannot talk while exercising, your exercise level is too intense. Intensity in exercise is how hard you work out. For example sprinting up a flight of stairs over and over again would be a high intensity workout. To measure the intensity of exercise one method would be to monitor the heart rate of the individual undertaking the exercise

This is what a calorimeter is used for simpler ex, to measure calories in food.

Ibelieve the answer above is c but im not sure