Answer:
Explanation: the question should be, Why is bulk flow a necessary condition of complex multicellularity?
Then here is the answer, Multicellular organisms are that have plenty cells and they have s complex units that makes up their functions and makes them to begin to function as one.
Organisms exhibiting complex multicellularity are big and have cells/tissues that are not usually in contact with their environment. They are have systems that can overcome the limits of diffusion (movement from area of higher concentration to that of lower) must evolve for basic physiologic processes to occur.
