What does FIN in TCP flag define?

A.
Used to close a TCP connection

B.
Used to abort a TCP connection abruptly

C.
Used to indicate the beginning of a TCP connection

D.
Used to acknowledge receipt of a previous packet or transmission

Explanation:
The FIN flag stands for the word FINished. This flag is used to tear down the virtual connections created using the previous flag (SYN), so because of this reason, the FIN flag always appears when the last packets are exchanged between a connection.