Determining How Far the Breakdown on a WBS Should Go

Determining how far the breakdown on a WBS should go (circle one) :

A) depends upon what is needed to get a good work definition and good time and cost estimates.
B) is arbitrary.
C) depends upon the functional areas in the project since the WBS is usually functionally divided.
D) should depend on how much effort the project manager is willing to devote to the WBS process.