Final answer:
The least likely entry point for subs on a monolithic slab is hollow block.
Step-by-step explanation:
The least likely entry point for subs on a monolithic slab is C. Hollow block. A monolithic slab is a type of foundation that consists of a single, continuous pour of concrete without any joints or seams. Plumbing can be installed through the slab, but it is a common entry point. Slab cracks are also a potential entry point. Additions, such as doorways or windows, may be made after the slab is poured and can provide an entry point for subs.