A landlord entered into a written four-year lease with a tenant for an apartment in the landlord's apartment house. The tenant's lease, and all leases in the apartment house, prohibited the playing of musical instruments between 10 p.m. and 8 a.m. The lease required the tenant to pay the rent on a monthly basis. Two years into the lease, the tenant assigned the lease to a nurse with the landlord's permission. The nurse then assigned the lease to his brother with the landlord's permission. The brother went into possession. A neighboring tenant in the same apartment house insisted upon playing a trumpet in a loud manner between 2 a.m. and 4 a.m. The brother complained to the landlord without success. Unable to sleep each night, the brother abandoned his apartment after occupying it for two months. If the landlord sues the nurse for the rent due during the period after the nurse's brother left, what would be the nurse's best defense? Question 12 options: a) A breach of the landlord's covenant of quiet enjoyment. b) Estoppel, because the landlord consented to a further assignment. c) Lack of privity of estate. d) Constructive eviction