What happens to K's ownership of the apartment building after U's death?

The correct answer indicates that K will continue to own the same undivided interest in the apartment building after U's death. In real estate, when two or more parties co-own a property as tenants in common or in some forms of joint tenancy, the death of one owner does not necessarily terminate the ownership rights of the surviving co-owners. Instead, the undivided interest of the deceased owner typically passes according to the terms of a will or applicable inheritance laws.

In this scenario, K retains their ownership share, meaning their rights and responsibilities regarding the property remain intact, regardless of U's passing. This is foundational in property law, where ownership shares are considered undivided, allowing surviving co-owners to maintain their interest in the property as it was prior to the death of their co-owner. The situation differs depending on the type of ownership structure or any legal documents, such as a will, but in this context, K's ownership remains consistent and unchanged.