Understanding Earth's Water Coverage
The Earth is often referred to as the "Blue Planet" due to its vast oceans and water bodies. Approximately **71%** of the Earth's surface is covered by water, which is roughly three-fourths of the entire planet.

Key Points:
- Oceans: About 96.5% of all Earth's water is found in the oceans, which play a crucial role in regulating the planet's climate and weather patterns.
- Other Water Bodies: The remaining percentage is made up of freshwater sources such as rivers, lakes, glaciers, and groundwater.
- Impact of Water: Water is essential for all forms of life and influences various ecosystems. It supports biodiversity and is vital for agriculture, industry, and human consumption.

Why "Three-Fourths"?
- Since the Earth's total surface area is about 510 million square kilometers, the water-covered area is approximately **361 million square kilometers**. This substantial coverage highlights the dominance of water in shaping the planet's geography.
- The large amount of water affects weather patterns, ocean currents, and even the Earth's geology through processes like erosion and sedimentation.

Conclusion
In conclusion, the correct answer is option 'C' as approximately three-fourths of the Earth's surface is covered by water. This fact emphasizes the importance of water in sustaining life and maintaining ecological balance on our planet.