The part of the earth crust covered by water bodies is known as the

Step 1: Analyze the question The question asks for the name given to the part of the earth that is covered by water bodies such as oceans, seas, rivers, lakes and ponds.

Step 2: Explain the concepts Let's look at each option:

• Sial: The upper layer of the earth's crust, made mostly of silica and aluminium (Si + Al). It forms the continents, so it is rock, not water.
• Stratosphere: A layer of the atmosphere above the troposphere. It contains the ozone layer and has nothing to do with water bodies on the earth's surface.
• Atmosphere: The envelope of gases surrounding the earth.
• Hydrosphere: The water part of the earth, which includes oceans, seas, lakes, rivers, underground water and even ice caps. The word comes from the Greek hydro meaning "water".

Step 3: Solve The question is about the part of the earth's surface covered by water. Only the hydrosphere fits this description.

• Sial is rock (continental crust), so it is eliminated.
• Stratosphere and atmosphere are gaseous layers, so they are eliminated.
• Hydrosphere refers to all the water bodies, so it is correct.

Answer: D. hydrosphere

Exam Tip: Remember the "spheres" using their Greek prefixes:

• Litho = rock → lithosphere
• Hydro = water → hydrosphere
• Atmo = vapour/gas → atmosphere
• Bio = life → biosphere

If you see "water" in a question about the earth's spheres, think hydro, as in "hydroelectric power" and "dehydration".