According to the theory of constraints, a stockpile of work in process inventory should be stored A) as a buffer only in front of the constrained operation to keep it operating if there is a slowdown in a subsequent operation. B) as a buffer only in front of the constrained operation to keep it operating if there is a slowdown in a previous operation. C) as a buffer at all stages of the process to keep them operating in the event there is any disruption anywhere in the process. D) nowhere. There should be no work in process inventories