CONCENTRIC spherical layers subdividing the Solid earth. It consists of an outer silicate solid crust, a highly viscous asthenosphere and solid mantle, a liquid outer core whose flow GENERATES the Earth's magnetic field, and a solid inner core.The Moho is the boundary between the crust and the mantle in the earth. This is a DEPTH where seismic waves change velocity and there is also a change in chemical composition. Also termed the Mohorovicic discontinuity after the Croatian seismologist Andrija Mohorovicic (1857-1936) discovered it. The boundary is between 25 and 60 km deep beneath the continents and between 5 and 8 km deep beneath the ocean floor.Hence, the correct answer is Mohorovicic discontinuity.There are five discontinuities inside the earth:Conrad Discontinuity: TRANSITION ZONE between SIAL and SIMA.Mohorovicic Discontinuity: Transition zone between the Crust and Mantle.Repiti Discontinuity: Transition zone between Outer mantle and Inner mantle.Gutenberg Discontinuity: Transition zone between Mantle and Core.Lehman Discontinuity: Transition zone between Outer core and Inner core.