Choice "B" is correct. When electronic data is not maintained indefinitely, the auditor must be careful to consider the appropriate timing for audit tests, making sure that testing is performed while data is still available.
Choice "d" is incorrect. The auditor determines the acceptable level of detection risk based on the assessed risk of material misstatement (inherent risk and control risk). Assessed risk is not dependent on the length of time electronic evidence is available.
Choice "c" is incorrect. Whether to adopt substantive or reliance test strategies (i.e., a substantive approach or a combined approach) is not dependent on the length of time electronic evidence is available.
Choice "a" is incorrect. The assessed level of inherent risk is based on the nature of the underlying assertion, and not on the length of time electronic evidence is available.