Which one of the following statements is correct regarding blood pressure?

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?

$ECG$ records:

$ECG$ is a graphical representation of the electrical activity of the heart during

Arrange and select the following events in the correct sequence during the measurement of blood pressure by a sphygmomanometer.
$i.$ Pulsatile sound disappears.
$ii.$ Cuff is inflated to block the brachial artery by external pressure.
$iii.$ First pulsatile sound is heard indicating systolic pressure.
$iv.$ Pressure in the cuff is slowly lowered.
$v.$ Cuff is wrapped tightly around the upper arm.

Given below are two statements.
Statement $I$ - Graphical recording of electrical variations detected at the surface of body during their propagation through the wall of heart is electrocardiograph.
Statement $II$ - The instrument used for the graphical recording of electrical variations detected at the surface of body during their propagation through wall of heart is electrocardiogram.
In the light of above statements,select the correct option given below: