Where is the answer choice?
D. clear
an adjective describes a noun and clear is describing the waters
"A coherent narrative will be easy to follow and more enjoyable for your reader." Looking at this, we see the words, "easy to follow," and, "more enjoyable." These are our clue words. We can rule our both A, B and D because none fit in as a definition referring to easy. C, however, fits the definition and this is your answer.
"A 'connected' narrative will be easy to follow and more enjoyable for your reader."
The answer would be D, since a quartet means 4, and a triumvirate means 3. So again the answer is 4:3.