.................... refers to the art of protecting information by transforming it into an unreadable format.

Cryptography

The correct answer is option 3- Cryptography.

Data may be intercepted in the course of transmission. For this, one may use cryptography. It refers to the art of protecting information by transforming it (encrypting it) into an unreadable format called ‘cyphertext’. Only those who possess a secret key can decipher (or decrypt) the message into ‘plaintext’. This is similar to using ‘code words’ with some one so that others do not understand your conversation.