Which of the following is an example of mutualism? a. a group of piranhas work together to attack a large animal. b. a mosquito feeds off the blood of another animal and leaves an itchy bump. c. barnacles attach themselves to the bottom of a boat for transportation. d. a sea sponge attached to a crab the crab hide from predators and gains transportation for itself.

the answer for apex is "1 and 6"

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.