I called USCIS and ask why my case is delayed so long time, and 3 weeks later, got the email as following:
The status of this service request is:
Service records show your case is currently waiting to be reviewed by
an officer. You will receive a decision or notice of other action once
your case is adjudicated.
Then how long it will take them to process the case? Does this mean NC is done?
A lot of thanks to this bulletin board