In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives._x005F_x000D_ Division of labor is the law in the organic world as in the industrial. Animals ___________ the lowest type, such as the amoeba, do not have separate organs for respiration, digestion, assimilation, elimination, etc. But in the ___________ forms each organ not only has its own specific work, but even within the same organ each part has its own particular function assigned. __________ we have seen that the _________ parts of the neurone probably perform different functions, the cells  generating energy and the fibers ______________ it._x005F_x000D_ Animals ___________ the lowest type,_x005F_x000D_

• A. form
• B. for
• C. of
• D. at