The earth’s crust is the thinnest

The correct answer is Option 3.

The Earth's crust is divided into two types: Continental and Oceanic. The thickness varies significantly based on geological composition and location:

• Oceanic Crust (Option 3): It is the thinnest layer, averaging only 5 to 10 km in thickness. It is composed of dense basaltic rocks, making it sit lower in the mantle.
• Continental Crust (Option 2): This is much thicker, averaging 30 to 50 km.
• Mountain Ranges (Option 1): The crust is thickest here, reaching up to 70 to 100 km due to "roots" that support the weight of the mountains.
• Mid-oceanic ridges (Option 4): While the lithosphere is thinnest here, the crustal layer itself is already part of the thin oceanic floor.

Therefore, the crust reaches its minimum thickness at the ocean bottoms, where the distance between the seafloor and the Moho boundary is shortest.