The Picket Fence Metaphor Is an Appropriate Description of Current

The picket fence metaphor is an appropriate description of current American federalism because

A) different policy areas are "fenced" off from each other by congressional action and court rulings.
B) it takes money to make policy, just like it does to build a fence.
C) policy makers mainly interact with others in the same policy area, regardless of whether they are federal or state employees.
D) the state and federal governments have clear boundaries, much like two fences on separate properties.