From the diagram of the rock cycle the missing part is ( B ) ; Melting
Magma is a hot liquid/semi-liquid rock that is usually formed under the earth due to high pressure and temperature present in the inner core of the earth. magma is obtained by the melting down of existing rocks ( Igneous, sedimentary and metamorphic rocks ) under high pressure and temperature in the earths core.
Magma is released to the earth surfaces during volcanoes therefore the missing term in the rock cycle is melting
Hence we can conclude that from the diagram of the rock cycle the missing part is Melting.
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