The correct answer is - B. Slope of the land.
The watersheds are defined by the slopes. They can be small, medium sized, or very large. All parts of the land on planet Earth belong to one watershed or another.
The watersheds have boundaries, and those boundaries are along the highest points of the mountains or the hills. In most cases, one of the slopes of the mountain or hill is in one watershed, while the other one is in another watershed.
The water from the watershed goes into a single place as its final destination. The water can run down the slope on the ground after a heavy rainfall, get into smaller streams and rivers, get directly into a bigger river, but in the end all of that water will get to the biggest water body in the watershed.
