Which of the following values indicates hypertension?

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

Which of the following is a repolarization wave?

Describe in detail: $ECG$.

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?

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