Option B (200–2,000m) is the correct answer. The textbook context describes the four major divisions of the ocean floor in sequence: Continental Shelf, Continental Slope, Deep Sea Plain, and Oceanic Deeps. From the context, the Continental Shelf has depths varying from 30m to 600m, and the Deep Sea Plains are found between 3,000-6,000m below sea level. The Continental Slope lies between these two features, starting after the shelf break (where the shelf ends at around 200-600m depth) and extending down to the deep sea plains. Therefore, the average depth of the continental slope varies between 200–2,000m, making option B the correct choice.