In the ocean, what is a landform similar to a valley known as? a) it is known as a rift. b) it is known as the ocean basin. c) it is known as the mid-ocean ridge. d) it is known as an underwater valley.

1. crust 1 the metallic layer at the earth's center 2. inner core 3 the firm layer between the crust and the asthenosphere 3. lower mantle 2 the layer surrounding the inner core 4. asthenosphere 4 the semi-solid layer between the top layer and the upper mantle 5. upper mantle 5 the layer between the asthenosphere and lower mantle 6. top layer 6 the earth's outermost layer 7. outer core 7 the hottest part of the mantle