Final answer:
Data encryption is the security feature used in Bluetooth device pairing to ensure that data exchanged between devices is protected and cannot be intercepted by unauthorized users.
Step-by-step explanation:
The security feature used in Bluetooth device pairing is a) Data encryption. When two Bluetooth devices pair, they establish a connection that is secured through the use of encryption. This encryption ensures that the data exchanged between the devices cannot be readily intercepted or understood by unauthorized users. Encryption is a critical component of Bluetooth security protocols such as Secure Simple Pairing (SSP), which uses a variety of methods to generate and exchange keys to create a secure connection.