Which of the following is a form of multiple ownership in which each owner possesses an undivided proportional interest in the entire property, although the ownership shares need not be equal?

Tenancy by the entirety is a form of joint ownership available only to married couples, where both partners have equal rights to the property. This type of ownership includes a right of survivorship, meaning that if one spouse dies, the other automatically inherits the deceased spouse's share. It does not permit unequal ownership interests, distinguishing it from tenancy in common.

Tenancy at will is a rental arrangement where a tenant occupies a property with the landlord's consent but without a formal lease agreement. This form of ownership provides no security or defined ownership interest in the property itself; rather, it is a temporary arrangement that can be terminated by either party. It does not involve multiple owners or proportional interests in property.

Joint tenancy is a type of ownership where two or more individuals hold equal shares in a property, characterized by the right of survivorship. In joint tenancy, if one owner dies, their share is automatically transferred to the surviving owners. Unlike tenancy in common, joint tenancy does not accommodate unequal ownership interests, making it distinctly different.