The correct option is
A Process of coming out of WBC through the capillary wall to fight against foreign micro-organism
Diapedesis is the process of coming out of WBC through the capillary wall to fight against foreign microorganism.
Diapedesis - The movement or passage of blood cells, especially white blood cells, through intact capillary walls into surrounding body tissue. Also called migration.
The movement of white blood cells and other cells out of small arterioles, venules, and capillaries as part of the inflammatory response. The cells move through gaps between cells in the vessel walls.
So, the correct answer is option B.