Choice "B" is correct. The assessment of control risk is based on auditor judgment. A computer cannot replace professional auditor judgment in assessing control risk.
Choice "c" is incorrect. Computer software would be used when constructing parallel simulations. Parallel simulation involves taking the client's data and reprocessing it using the auditor's equipment and software.
Choice "a" is incorrect. The auditor would use generalized audit software or retrieval package software to access client data files.
Choice "d" is incorrect. The auditor would most likely use some sort of software to prepare spreadsheets.