Final answer:
An easement by necessity is created when a landlocked parcel has no alternative access, not merely on request or at buyer's discretion.
Step-by-step explanation:
An easement by necessity is generally created when a parcel of land is landlocked and requires access to a public road. The correct scenario for creating an easement by necessity is if there's no alternative access (option b). This type of easement is not dependent on the owner's request, the buyer's discretion, or urban area specifications. Eminent domain is a separate issue where the government has the power to seize property for public use, with compensation to the owner, often used for infrastructure like roads or utilities, but it has recently been controversially used for economic redevelopment purposes.