I believe the answer is B. Nguyen explains how buses reduce traffic by lowering the number of cars on the road.
The passage says “Clearly, buses reduce traffic rather than cause it”. Answer B is the only answer that mentions traffic in a logical way.
I hope this helps!
The only preposition in this sentence is the word of.
Answer: It would be ocean's
Explanation: In this context the apostrophe show ownership, or WHOSE waters became choppy (I know an ocean is a WHAT and not a WHO but phrasing it like this in my mind always helped me). Without the apostrophe it would be the plural form of OCEAN.