Choice "B" is correct. The independent auditor's direct personal knowledge, based on personal inquiry and observation, are auditing procedures commonly used to test segregation of duties.
Choice "d" is incorrect. Test counts and cutoff procedures represent substantive tests, and they would not be used to test segregation of duties.
Choice "c" is incorrect. Analytical procedures and invoice recomputation represent substantive tests, and they would not be used to test segregation of duties.
Choice "a" is incorrect. Document inspection and reconciliation represent substantive tests, and they would not be used to test segregation of duties.