Choice "A" is correct. Audit documentation should be prepared in enough detail so that an experienced auditor who has no previous connection with the audit can understand the procedures performed and the evidence obtained.
Choice "d" is incorrect. The requirement is that audit documentation be detailed enough that an experienced auditor who has no previous connection with the audit can understand the procedures performed and the evidence obtained. This is a higher standard than simply requiring the audit documentation to be appropriate for an auditor who is already familiar with the client.
Choices "b" and "c" are incorrect. Readers of the financial statements typically would not have access to the audit documentation.