What is the imaginary line dividing drainage basins?

• A. Riverbed
• B. Watershed
• C. Confluence
• D. Clouds

Answer: (B)

The imaginary line dividing drainage basins is the drainage divide, which defines a watershed boundary. This high ground, often following ridges, separates where precipitation drains into one river system from where it drains into another. A watershed is the land area that funnels water toward a specific outlet, so the edge of that area—the divide—marks the split between basins. The other options don’t fit: a riverbed is the channel that carries water, a confluence is where two streams meet, and clouds are part of the atmosphere, not the boundary between drainage basins.