Ans: The normal flow of events describes the steps that are normally executed in a use case. The steps in a normal flow are listed in the order in which they are performed. In some cases it is recommended that the steps in a normal flow be decomposed to simplify the normal flow. Thus, subflows are used to help keep the normal flow of events as simple as possible. Subflows represent the decomposition of normal flow steps. At times, subflows could be replaced with a separate use case, if it makes sense.Response: See pages 170-171