The state of equilibrium in the body with respect to various functions and to the chemical composition of fluids and tissues is called

Choose the correct option:
$(1)$ Depolarization of the ventricles induces the $QRS$ / $T$ waves.
$(2)$ Incomplete double circulation is seen in reptiles / birds.

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

Intracellular fluid and extracellular fluid constitute what percentage of total body weight,respectively?

Hypokalaemia means

Oedema is defined as: