Which of the following is true of SITOR (NBDP) ARQ mode:

The ship station sends a group of 3 characters twice and then waits for an "RQ" signal to indicate proper receipt before transmission of the next 3 characters.

The Ship station sends each character twice, using a time diversity system to ensure proper parity.

The ship station sends a group of 3 characters, the shore station checks for proper parity and then requests the same group be resent to enable error correction.

The ship station sends a group of 3 characters, the shore station checks for proper parity. If parity is OK, the shore station indicates readiness for transmission of the next 3 characters.

Which of the following is true of SITOR...