Which instrument is used to measure blood pressure?

Systolic pressure in an adult human is

Which of the following sentences is correct?
$I$. $ECG$ is of a great clinical significance.
$II$. Electrocardiograph is the machine used to obtain an electrocardiogram.
$III$. To obtain a standard $ECG$,a patient is connected to the machine with $3$ electrical leads (one to each wrist and to the left ankle).
$IV$. Normal activities of the heart are regulated intrinsically (auto-regulated by nodal tissue).
$V$. Electrocardiogram is the graphical representation of the electrical activity of the heart during a cardiac cycle.
Which of the following options contains all the correct statements?

Systolic pressure in a normal human is

Match the Column $-I$ with Column $-II$.

Column $-I$	Column $-II$
$(a) \; P-$wave	$(i) \; \text{Depolarisation of ventricles}$
$(b) \; QRS$ complex	$(ii) \; \text{Repolarisation of ventricles}$
$(c) \; T-$wave	$(iii) \; \text{Coronary ischemia}$
$(d) \; \text{Reduction in the size of } T-$wave	$(iv) \; \text{Depolarisation of atria}$
	$(v) \; \text{Repolarisation of atria}$

Select the correct option:
$(a) \quad (b) \quad (c) \quad (d)$

Given below is the $ECG$ of a normal human. Which one of its components is correctly interpreted below?