In a standard $ECG$,what does the $QRS$ complex represent?

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.

Systolic pressure is higher than diastolic pressure because

Write the differences between $P$-wave and $T$-wave.

In all the leads of $ECG$,all following are positive waves except

$T$-wave represents: