According to the SAP Help Portal1, one of the ways to specify on which system and client the control is executed is to assign a risk definition to the control for the desired system. The risk definition contains the connector information that determines the system and client where the control runs. Therefore, A is the correct answer. B, C, and D are not valid ways to specify the system and client for control execution, as they are related to other aspects of control configuration, such as approval, reporting, and rule set assignment. Reference: 1 https://help.sap.com/doc/e2ccae7ee6354b169cf845cd665e07fe/1.0%202016-07/en-US/frameset.htm?frameset.htm