The correct answer is - B. The rock formed in a fast moving stream.
The rocks that have ripples are a relatively easy when it comes to guessing where they formed and under what conditions. The reason for that are the ripples themselves, as they are formed only because of the influence of water or wind, though it is mostly the water.
If we see a rock with ripples, the chances are that that rock has formed in place where it was influenced by water for prolonged period of time. The best guess would be a fast moving stream, as the water will have bigger power, and will be able to have bigger influence on the rock and make its ripples.
