Choice "B" is correct. The accountant-client privilege can be claimed only in those states that recognize the privilege.
Choice "d" is incorrect. Generally, there is no federal accountant-client privilege. There is a limited federal privilege for noncriminal tax proceedings other than tax shelter matters, but here the engagement was for audit services, and the proceeding is a criminal proceeding.
Choice "a" is incorrect. If a state has enacted the privilege, the privilege is not limited to civil cases.
Choice "c" is incorrect. Where the privilege exists, it would prevent testimony about the audit, not limit testimony to the audit.