Which boundary description correctly matches constructive boundaries?

• A. Two plates move towards each other
• B. Two plates move away from each other
• C. Two plates slide past each other
• D. One plate sinks below another

Answer: (B)

Constructive boundaries are the places where new crust is created as plates separate. At these divergent boundaries, the two plates move apart, opening up space that mantle magma can rise into. When this magma cools, it solidifies to form new lithosphere, driving the creation of new crust and often causing seafloor spreading at mid-ocean ridges or rift valleys on land. This is why the boundary description that states two plates move away from each other fits as constructive. The other scenarios describe boundaries where crust is destroyed or simply slides past, which do not create new crust.