Name That Client

At a grand jury probe into conspiracy to commit income tax violations, the state calls three persons, each of whom is a duly licensed and practicing attorney. The purpose of calling them is to obtain the names of certain unknown conspirators who, among other things, met with the attorneys to secure representation for the named and indicted conspirators.

The U.S. Attorney asks each attorney the following questions:

(1) Did any of the named defendants employ you to represent him?

(2) Did any third party make arrangements for you to represent a named defendant? If so, who?

(3) If you posted bond for a named defendant, who furnished the bond money?

(4) If you have been paid any attorney's fees on behalf of a named defendant, who paid them?

Which, if any, of these questions may be successfully resisted on grounds of privilege? When the attorney-client privilege is asserted and contested, where does the burden of proof lie?