Which of the following vertebrate organs receives only oxygenated blood?

What is the correct order of events occurring in blood clotting?
$I.$ Conversion of fibrinogen to fibrin
$II.$ Formation of clot
$III.$ Thromboplastin formation
$IV.$ Conversion of prothrombin to thrombin
Choose the correct option.

Match the following:
Types of leucocytes | Function
$A.$ Neutrophils | $1.$ Heparin and histamine secretion
$B.$ Basophils | $2.$ Antibodies formation
$C.$ Acidophils | $3.$ Scavenger
$D.$ Monocytes | $4.$ Phagocytes
$E.$ Lymphocytes | $5.$ Antiallergic and healing of wounds
The correct pairing sequence is:

Which of the following cardiac effects can be observed if the potassium concentration is increased two to three times the normal value?

Describe the events in the cardiac cycle. Explain 'double circulation'.

Plethysmograph is used to measure