Bill owned in fee simple Lot 1 in a properly approved subdivision, designed and zoned for industrial use. Gail owned the adjoining Lot 2 in the same subdivision. The plat of the subdivision was recorded as authorized by statute. Twelve years ago, Bill erected an industrial building wholly situated on Lot 1 but with one wall along the boundary common with Lot 2. The construction was done as authorized by a building permit, validly obtained under applicable statutes, ordinances, and regulations. Further, the construction was regularly inspected and passed as being in compliance with all building code requirements. Lot 2 remained vacant until six months ago, when Gail began excavation pursuant to a building permit authorizing the erection of an industrial building situated on Lot 2 but with one wall along the boundary common with Lot 1. The excavation caused subsidence of a portion of Lot 1 that resulted in injury to Bill's building. The excavation was not done negligently or with any malicious intent to injure. In the jurisdiction, the time to acquire title by adverse possession or rights by prescription is 10 years. Bill brought an appropriate action against Gail to recover damages resulting from the injuries to the building on Lot 1. In such lawsuit, judgment should be for 
Bill, if, but only if, the subsidence would have occurred without the weight of the building on Lot 1.  Bill, because a right for support, appurtenant to Lot 1, had been acquired by adverse possession or prescription.  Gail, because Lots 1 and 2 are urban land, as distinguished from rural land and, therefore, under the circumstances Bill had the duty to protect any improvements on Lot 1.  Gail, because the construction and the use to be made of the building were both authorized by the applicable law. 