When plants take in carbon it can be released back in the atmosphere through cellular respiration, eaten by animals in the form of sugar, or
released back into the ground through decomposition
released back into the atmosphere
through photosynthesis

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.

i believe the answer would be b. hope it : )