Which one of the following is found in the innermost part of the Earth ?

The Earth's interior is divided into several layers based on chemical and rheological properties, separated by specific boundaries known as discontinuities. These discontinuities are identified by changes in the velocity of seismic waves.

• Conrad Discontinuity: Located between the upper and lower crust.
• Mohorovicic (Moho) Discontinuity: Separates the crust from the underlying mantle.
• Gutenberg Discontinuity: Marks the boundary between the lower mantle and the outer core (at approximately 2,900 km depth).
• Lehmann Discontinuity: This is the boundary between the liquid outer core and the solid inner core (at approximately 5,150 km depth).

Since the inner core is the deepest part of the Earth, the Lehmann discontinuity is found in the innermost part of the Earth among the given options, making Option D correct.