The answer is D: Covering your ideas in a logical, step-by-step manner that the reader can follow.
Although the expression is equivocal, to follow a natural order when writing refers to the concatenation, coherence, and logic of the ideas put together through phrases. If analyzed, each idea conveyed in a text can be broken down into its component parts, these can be placed in a “natural order”, that is to say, joined one after the other, so that their linear conjunction, as a whole, makes sense.