Of the choices given above, the one that is not a part of the President's Cabinet is B, the US Solicitor General.
The Cabinet is made up of the heads of the various executive departments and of a few other high officials such as the White House Chief of Staff and the US Trade Representative. The Solicitor General of the United States is not a department head. Instead, he or she is part of the Department of Justice. The head of the Department of Justice is the Attorney General, who is a member of the Cabinet.