Which characteristic best explains why carbon is relevant to living organisms?"
Carbon is the most common element on Earth
Carbon can form a wide variety of molecules
Many carbon isotopes are radioactive
Many carbon allotropes occur in nature.

Carbon is the foremost common element on Earth. Carbon can form a wide assortment of molecules.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.