Which of the following cells phagocytose microorganisms rapidly?

Consider the following four statements regarding the human circulatory system:
$(a)$ Arteries have thick walls and have a smaller lumen compared to veins.
$(b)$ Angina is a sudden chest pain.
$(c)$ In the $ABO$ blood grouping system,a person with $AB$ blood group can donate blood to anyone.
$(d)$ Calcium ions play an important role in blood clotting.
Which two of the above statements are correct?

The process of blood clot formation within the circulatory system is known as:

Which organ is responsible for the storage of blood to be released during sudden blood loss?

If cardiac output is $4200 \text{ ml/min}$,then $x$ beats/min is the heart rate and $y$ is the term for pulse rate.

$A$: Elevated levels of $Na^+$ decrease the heart rate and contractility.
$R$: Elevated $Na^+$ levels increase the excitability of the $SA$ node.