The answer is D. An estate at will
Estate at will is a type of tenancy agreement in which a tenant is given permission to occupy a property by the landlord for an unspecified amount of time, and can be asked to leave the property by the landlord at any time without notice. The agreement is generally oral, and there is no fixed term or specific end date. Estate at will can be terminated by either the landlord or the tenant at any time, without the need for a formal eviction process.