In which type of concurrent estate do both spouses hold an equal and undivided interest?

The correct answer is tenancy by the entirety, which is a special form of concurrent ownership that is available exclusively to married couples. In this arrangement, both spouses have an equal and undivided interest in the property, which means that neither spouse can sell or transfer their share of the property without the consent of the other spouse. This form of ownership also provides certain protections. For instance, if one spouse incurs debt, the property cannot be used to satisfy that debt since both spouses own the property together.

Tenancy by the entirety is designed to reflect the unity and interdependence of marriage, thereby preventing unilateral actions regarding the property. It also includes a right of survivorship, meaning that if one spouse passes away, the other automatically becomes the sole owner of the property without the need for probate.

The other options represent different forms of property ownership. Tenancy in common allows multiple owners to hold separate but equal interests in the property without the right of survivorship. Joint tenancy, while also providing for equal interests and a right of survivorship, does not restrict ownership to married couples. Single ownership refers to property owned by one individual, contrary to the concept of concurrent estates.