In Hyperledger Fabric, the correct subcommand to add a peer to a channel ispeer channel join. This command is used by a peer node to join an existing channel. The command requires a block to be specified which typically is the genesis block of the channel, allowing the peer to synchronize with the channel's ledger from the beginning. Other commands likepeer channel fetch,peer channel create, andpeer channel updateserve different purposes.peer channel fetchretrieves blocks from a channel,peer channel createis used to set up a new channel, andpeer channel updatemodifies channel settings. Thus,peer channel joinis the specific command used to connect a peer to a channel.