Choice "B" is correct. As part of understanding internal control, an auditor is not required to obtain knowledge about the operating effectiveness of controls. Operating effectiveness is evaluated later, and only for those controls on which the auditor plans to rely.
Choice "c" is incorrect. Considering factors that affect the risk of material misstatement is a part of understanding internal control.
Choice "d" is incorrect. Ascertaining whether internal controls have been implemented is required as part of obtaining an understanding of internal control.
Choice "a" is incorrect. Identifying the types of potential misstatements that can occur is part of understanding internal control.