Choice "B" is correct. In a paperless system, the CPA would most likely need to continuously monitor and analyze transaction processing to ensure that controls were operating effectively throughout the period under audit. An embedded audit module is one way to achieve this goal.
Choice "c" is incorrect. While segregation of duties is an important control, there would be no reason to increase reliance on such controls in a paperless system.
Choice "d" is incorrect. Verification of encrypted digital certificates used to monitor the authorization of transactions would be used in all computerized systems.
Choice "a" is incorrect. Testing of firewall boundaries that restrict the recording of outside network traffic by itself does not ensure the completeness and accuracy of the financial data.