Answer : 2. "Blind carbon copy"
Explanation :

1. Blind carbon copy is the extended form of BCC used in e-mail communication.

2. It is used to send a copy of an email to a person without informing the recipient about it i.e. the identity of the recipient mentioned in the 'Bcc field' is hidden from other recipients receiving the same email.

3. Recipients in the BCC list can see every other email address, including the To and CC lists.