The correct option is It is the deepest part of the ocean floor..
Explanation
The continental shelf is the gently sloping seaward extension of the continental plate. It is the shallowest zone of the ocean floor, connecting the coast to the continental slope.
Analysis of the Options:
- It is the extended margin of each continent. is correct: The continental shelf is defined as the extended margin of each continent, occupied by relatively shallow seas and gulfs.
- It is covered with variable thicknesses of sediments. is correct: It is the site where sediments brought down by rivers, glaciers, and wind accumulate. Consequently, it is covered with variable thicknesses of sedimentary deposits.
- Massive sedimentary deposits here can be a source of fossil fuels. is correct: Massive sedimentary deposits on the shelf often trap organic matter, making these regions major sources of fossil fuels (petroleum and natural gas).
- It is the deepest part of the ocean floor. is incorrect: The continental shelf is the shallowest part of the ocean floor, with an average depth of approximately 200 meters. The deepest parts of the ocean floor are the oceanic trenches.
Key Takeaway: The continental shelf is the submerged edge of the continent characterized by shallow depths and rich resources, whereas oceanic trenches represent the deepest zones of the ocean relief.