Question

Choose the odd one out: basophils, neutrophils, monocytes, eosinophils.

Answer 1

WBCs are classified into two types: granulocytes and agranulocytes. Granulocytes which have granular cytoplasm and agranulocytes which do not have granular cytoplasm. granulocytes are further divided into three types: neutrophiles, basophils and eosinophils. Agranulocytes are divided into two types: lymphocytes and monocytes.

Complete answer :
To answer this question you must know about classification of White blood cells.
WBCs also called leukocytes are white colourless blood cells and its function is to provide protection in the body against various types of infection which can cause disease. They are classified into two main groups, granulocytes and agranulocytes depending on whether they contain granules in their cytoplasm or not.
granulocytes are three types basophils, neutrophils and eosinophils in which basophils are 8-10 micrometer in diameter, and it make up 0.5 to 1% of all white blood cells, neutrophils made up 60 -70% of all white blood cells and nucleus contain 2-5 lobes and eosinophils made up of all white blood cells having three lobes.
agranulocytes are divided into two types : monocytes and lymphocytes. Monocytes have kidney shaped nuclei and make up 3-8% of all white blood cells. lymphocytes are further divided into T cells, B cells and natural killer cells and leukocytes make up 20 -25 % of all WBCs, nucleus is round.
Since lymphocytes are types of agranulocytes and basophils,neutrophils and eosinophils are the types of granulocytes, therefore the correct option of the given question is monocytes.

Note:
WBCs (leucocytes) are formed in bone marrow from myeloid stem cells and some are formed in the lymph nodes from lymphoid stem cells. WBCs are also called as immunity developer cells as its major contribution to fight with different unwelcome pathogens. B Cells secrete antibodies to fight with pathogens and T cells attack the foreign invaders.