When using AES, note that both sender and receiver should share a cryptographic key which they don't share with anyone else to ensure that the message remains private. So$,$ if a team has $15$ individuals, how many unique AES keys are needed to support one$-$on$-$one private communication between any two team members using the system?

Question $13$ options:

$45$

$10$

$2$

$105$