The correct answer is Only 1 and 3. Discontinuities are the transition zones that separated the layers of the earth. Earth’s interior is made of different kinds of materials. Each of those materials is different from the others by their physical and chemical properties, such as temperature, density, etc. Discontinuity: • All those layers are separated from each other through a transition zone. • These transition zones are called discontinuities. • Conrad Discontinuity: It lies between the Upper crust and Lower crust. • Mohorovicic Discontinuity: It lies between crust and mantle. • Thus, statement 3 is correct. • Repiti Discontinuity: It lies between the Upper mantle and Lower mantle. • Gutenberg Discontinuity: It lies between core and mantle. • Lehman Discontinuity: It lies between the upper core and lower core. • Thus, statement 1 is correct. Related Concepts: Crust: • The uppermost layer over the earth’s surface is called the crust. • It is the thinnest of all the layers. • On the continental masses, It is about 35 km and on the ocean floors, only 5 km. • The density of the rocks found at the surface rocks: 2.7 - 2.9 gm/cm^(3) • The density of rocks found at the sea floor is around: 3.0 gm/cm^(3) • The oceanic crust is denser than the continental crust. • The crust is the thinnest layer of the Earth and it amounts to less than 1% of our planet's volume. • The earth is made up of several concentric layers with one inside another, just like an onion. • The crust is the outermost layer of Earth and is made up of igneous, metamorphic, and sedimentary rocks. • The Earth's crust is unstable because of the exogenic forces. Hence, statement 2 is incorrect that it's expressing the wrong information.