At which point is crust neither created nor destroyed?

island chain
mid-ocean ridge
divergent boundary
transform boundary

At divergent plate boundaries, new oceanic crust is formed. At convergent boundaries, old oceanic crust is destroyed. But at transform plate boundaries, crust is neither created nor destroyed :)

Transform boundary

Explanation:

Transform boundaries can be defined as the place where the tectonic plates slide on the side and past each other.

This is the place where there is no change in the lithosphere as it is neither created here nor destroyed here. Sea floor is a transform boundary.

Example: California's San Andreas fault is a transform boundary.