Which of the following statements concerning SITOR communications is true?

Correct Answer: Option A — ARQ transmissions are made in data groups consisting of three-character blocks.

In ARQ mode, data is transmitted in blocks of three characters. The receiving station checks the constant ratio of the 7-bit code (four ones and three zeros). If the ratio is incorrect, the receiver requests a repeat of that specific three-character block, ensuring high accuracy in point-to-point telex links.