Q.Which of the following WBCs are found in more numbers?
a. Eosinophil
b. Neutrophil
c. Basophil
d. Monocyte

Blood is a specialised fluid connective tissue that transports substances between every part of the body, made of two components: plasma, a liquid matrix that makes up about 55% of total blood volume, and the formed elements - red blood cells (erythrocytes), white blood cells (leucocytes) and platelets - which make up the remaining 45%. An average 70 kg adult carries roughly 5 litres of blood, and the fraction of that volume occupied by cells is called the haematocrit (packed cell volume). Red blood cells, at 4.5-5.5 million per cubic millimetre, vastly outnumber the other formed elements; they are biconcave, nucleus-free discs packed with the oxygen-carrying pigment haemoglobin and have a fixed 120-day lifespan before being broken down in the spleen. White blood cells, far less numerous at 6000-8000 per cubic millimetre, are nucleated, amoeboid defence cells split into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes), with neutrophils the most abundant type by far. Platelets are cell fragments from bone-marrow megakaryocytes, present at 1.5-3.5 lakh per cubic millimetre, whose job is to trigger clotting and plug injured vessels. Because blood constantly exchanges fluid, gases and nutrients with the interstitial fluid surrounding every cell, it is the single vessel-borne link that keeps distant tissues supplied and connected to the lungs, gut, liver and kidneys.