To use the pool at City Gym, one must have a membership there. Sarah has a membership at City Gym. She must ttherefore use the pool there at least occasionally. The reasoning in the argument is flawed in that the argument ['mistakes a policy that is strictly enforced for a policy to which exceptions are made', 'presumes that one or the other of two alternatives must be the case without establishing that no other alternative is possible', 'treats a statement whose truth is required for the conclusion to be true as though it were a statement whose truth ensures that the conclusion is true', 'concludes that a person has a certain attribute simply because that person belongs to a group most of whose members have that attribute']