Answer:
They would all not work they all work together.
Since there are no options listed to choose from, my best guess would be watches, since a lot of apple watch products are now sold with built in heart monitors.
A. A person is obese if he or she has an excess amount of body fat.
The reason for A and not B is because someone with a lot of muscles could weigh more based on their BMI, which doesn't differentiate between the weight from muscles vs. fat
The answer is d: check to see if the person is breathing normally