Which statement accurately describes an idle scan?

Which statement accurately describes an idle scan?

A.
A scanning method where "stealth" packets (packets without arty flags set) are sent from an attacker to a remote target host through IDS systems.

B.
A scanning method that scans all idle TCP connections on a remote target host to hijack them, so that you can take advantage of an authenticated data connection.

C.
A scanning method where long idle periods exist between the scanning packets sent so IDS systems do not sense the scan attack.

D.
A scanning method where a "zombie" host is used by an attacker to exploit a predictable IP fragmentation ID sequence and to discover open ports on the target host.