Choose the letter A, B, C or D to complete the passage below Approximately one-third of the Arctic Ocean is underlain by continental shelf, (6) _______ includes a broad shelf north of Eurasia and the narrower shelves of North America and Greenland. Seaward of the continental shelves lies the Arctic Basin proper, which is subdivided (7) _______ a set of three parallel ridges and four basins (also known as deeps). These features were discovered and explored in the late 1940s. The Lomonosov ...

Choose the letter A, B, C or D to complete the passage below

Approximately one-third of the Arctic Ocean is underlain by continental shelf, (6) _______ includes a broad shelf north of Eurasia and the narrower shelves of North America and Greenland. Seaward of the continental shelves lies the Arctic Basin proper, which is subdivided (7) _______ a set of three parallel ridges and four basins (also known as deeps). These features were discovered and explored in the late 1940s. The Lomonosov Ridge, the major ridge, cuts the Arctic Basin almost (8) _______ half, extending as a submarine bridge 1,800 km (1,100 mi) by Siberia to the northwestern tip of Greenland. Parallel with it (9) _______ two shorter ridges: the Alpha Ridge on the North American side, defining the Canada and Makarov basins, and the Arctic Mid-Ocean Ridge on the Eurasian side, forming the Nansen and Amundsen basins. The average (10) _______ of the Arctic Ocean is only 1,300 m (4,300 ft) because of the vast shallow expanses on the continental shelves. The deepest point in the Arctic Ocean is 5,450 m (17,880 ft).

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