Can't be M-D because question specifically states "Each Warehouse record has a distinct record owner". By the way, does anyone else wonder if John is an actual person? :)
When we define relationship in salesforce through custom fields there is no One-to-Many or Parent-Child relationship. It can be either Lookup or Master-Detail relationship. Also, in salesforce Child record of a Master-Detail relationship can't have owner. Here Warehouse is child to Account. As the question says warehouse has distintct owner, the answer should be Lookup. Please fixt the answer.
Its been asked that warehouse record has a distinct record owner which is related to parent, so it should be look up relationshipas in master detail relationship detail object do not have owner and master object controls all visibility setting of child object.