His muscles are getting stronger and have to break down to do so and that process hurts.
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.
I would say C, schizophrenia,
because schizophrenia is "a mental disorder that in many ways centers around not recognizing what is part of reality – namely, having psychotic breakdowns." It is not related to anxiety, as anxiety is classified as "neurotic" while schizophrenia is classified as "psychotic".
Hangovers are the body's adverse reaction
