The inability to concentrate, irritability, a rapid heart rate, and headaches are all signs of
a. stress
b. heart attack
c. decrease in adrenaline
d. all of the above

The correct answer is A.

These are all signs that the person is suffering from stress that is affecting their body physically. Stress has many effects on the body such as those listed, it can also take the form of anger, sadness, irrationality, sleep problems, physical aches and pains in different parts of the body, anxiety and so forth.