What is a continental shelf?

Answer: (d) It is a part of the continent that is submerged in relatively shallow sea

The shelf is the gently sloping, shallow-water edge of a continent.

The idea

A continent continues below the shoreline before the sea floor descends more steeply. Its submerged shallow margin is part of the continent, not a separate island. The shelf ends at the shelf break and is followed by the continental slope.

Coastline marks the land-water boundary → Shallow continental shelf extends offshore → Shelf break steepens the sea floor → Continental slope descends → Continental rise may lead to the deep ocean floor

Why the others are wrong

(a) Close, but (d) is the standard definition.

(c) That is an island.

The trap

(a) and (d) say similar things — (d) is the textbook wording.

Also know

Shelf width varies greatly: it is often broad on passive margins and narrow near active plate margins. Shelves support important fisheries and can contain oil and gas. The legal continental shelf under maritime law is not identical to the shallow geomorphic shelf. An island is land above water surrounded by water.