The given graph shows heart rates of three persons X, Y and Z under different conditions over time. Select the correct option regarding it.
APerson X is a dead person whereas persons Y and Z are suffering from different heart diseases.
BPerson X is sleeping, person Y is exercising whereas person Z is having irregular heartbeat due to some heart dysfunction.
CPerson X is going through a heart attack whereas person Z has healthy heart showing changes in heart rates while walking.
DNone of these