Books and records of a taxpayer may be examined by the Service provided that:

a) they are relevant to the Service's inquiry and are protected by the attorney-client privilege.

b) they are relevant to the Service's inquiry and not protected by the tax advice privilege granted under Code Sec. 7525.

c) they are relevant to the Service's inquiry and not protected by the accountant-client privilege.

d) they are relevant to the Service's inquiry and the documents do not include written communications about participation in a tax shelter.