(A) is incorrect if we look at lines 9-18. We see that in these lines, the author brings up a point of view that suggests there are these distinct, individual modules. She then immediately calls this view into question at the beginning of the next paragraph, and devotes the remainder of that paragraph to refuting the idea. Note that in lines 35-37, the author notes that "rate of oxygen use...stands as a measure of metabolic activity." This lends direct support to (C). Hope this helps!
