Right option is (b) Single twisted pair cable with shielding
Easiest explanation: The MIL STD 1533 bus is formed as a single twisted cable pair with one layer of shielding and jacketing and with a maximum length of 100 m (328 ft). Although direct coupling to the bus is allowed, this is generally not used in order to avoid the risk of one terminal shorting out the bus. The bus connection is typically via a transformer coupled stub so that shorting of the stub is isolated from the bus.
