Arrange the following discontinuities in correct order from earth surface to core:
A. Gutenberg
B. Moho
C. Lehman
D. Conrad
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Question

Arrange the following discontinuities in correct order from earth surface to core: 
A. Gutenberg 
B. Moho 
C. Lehman 
D. Conrad
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Accepted Answer

The correct order of discontinuities from the Earth's surface to the core is D, B, A, C, which corresponds to Option 3. Here's why:

*   **D. Conrad Discontinuity:** This discontinuity lies within the continental crust, separating the upper (sialic) crust from the lower (simatic) crust. It's the shallowest of the listed discontinuities.

*   **B. Moho (Mohorovičić) Discontinuity:** This marks the boundary between the Earth's crust (both oceanic and continental) and the mantle. It's significantly deeper than the Conrad discontinuity.

*   **A. Gutenberg Discontinuity:** This is a major boundary located between the Earth's mantle and the outer core. It's much deeper than both the Conrad and Moho discontinuities.

*   **C. Lehman Discontinuity:** This discontinuity is found within the Earth's core, specifically separating the liquid outer core from the solid inner core. It's the deepest of the listed discontinuities.

Therefore, the order from the surface to the core is Conrad, Moho, Gutenberg, and Lehman, making Option 3 (D, B, A, C) the correct answer.

Now, let's explain why the other options are incorrect:

*   **Option 1 (A, B, C, D):** This places the Gutenberg discontinuity (mantle-outer core boundary) closest to the surface, which is incorrect. The Moho, Lehman, and Conrad discontinuities are all shallower.

*   **Option 2 (A, C, B, D):** This places the Gutenberg discontinuity closest to the surface, followed by the Lehman discontinuity. This is incorrect as the Moho and Conrad discontinuities are shallower.

*   **Option 4 (D, C, B, A):** This places the Conrad discontinuity closest to the surface, which is correct, but then incorrectly places the Lehman discontinuity (inner core boundary) before the Moho and Gutenberg discontinuities.