Answer:
A) absolutely liable for any collapse.
Step-by-step explanation:
As the owner of the land, Abigail, is the owner of both the surface and mineral rights of the land, but she probably sold or leased the mineral rights to Umberto. Mineral rights refer to the excavation rights of a property that allow a business to look for oil, gas, minerals, etc.
Mineral rights authorize Umberto to excavate and look for oil or minerals, but his actions cannot affect the surface. The surface rights are still owned by Abigail, so Umberto is liable for any damages suffered by surface structures.