What is referred to as owning all ownership interests in real property?

Owning all ownership interests in real property is referred to as legal title. Legal title signifies that the owner has the formal right to the property, allowing them the authority to control it, sell it, or transfer it. This ownership is recognized by law and provides the holder with full rights associated with that property, such as possession and use.

In contrast, equitable title represents a person's interest in a property, which may not come with the full legal rights. Leasehold interest grants rights for a specific period under a lease agreement but does not comprise full ownership of the property. Underlying title pertains to interests in property that may not be readily apparent, and it typically involves various layers of ownership or claims that may exist below the primary ownership structure.

Thus, legal title is the most comprehensive form of ownership that encompasses all interests in real property, making it the correct choice.