In general, which of the following statements is correct with respect to ownership, possession, or access to working papers prepared by a CPA firm in connection with an audit?

a. The working papers may be reviewed by third parties pursuant to a PCAOB inspection.

b. The working papers are never allowed to be reviewed by anyone outside of the firm that prepared them.

c. The working papers are the property of the client after the client pays the fee.

d. The working papers must be retained by the CPA firm for a period of ten years.