There is nothing is mail standards about it. If you want to ask anyone about anything, just do it. But CC is a separate header with just address(es). If your mail message has "attachments", it will be sent to CC addresses as well. Note, that nothing is actually "attached". "Attachment" is nothing but a "part" in a multi-part message. As the whole message is sent somewhere, it is sent as a whole.
Please see: http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html