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

What is blood pressure?

Match List $I$ with List $II$.

List $I$	List $II$
$A$. $P$-wave	$I$. Beginning of systole
$B$. $Q$-wave	$II$. Repolarisation of ventricles
$C$. $QRS$ complex	$III$. Depolarisation of atria
$D$. $T$-wave	$IV$. Depolarisation of ventricles

Choose the correct answer from the options given below:

$X-$ In $ECG,$ $P-$ wave represents the electrical excitation of the ventricle.
$Y -$ $QRS$ waves represent depolarization of atria.

What is represented by the $P$-wave in an $ECG$?

Complete the missing words in the statements given below:
$(a)$ Plasma without clotting factors is called serum.
$(b)$ $.........$ and monocytes are phagocytic cells.
$(c)$ Eosinophils are associated with $.........$ reactions.
$(d)$ $.........$ ions play a significant role in clotting.
$(e)$ One can determine the heart beat rate by counting the number of $.........$ in an $ECG$.