In digital communications, the serial format for transmitting binary information uses how many conductors in the link, and what is the key idea behind this method?

Introduction / Context:
Serial transmission is a foundational concept in digital electronics and data communications. This question checks whether you understand that, in a serial link, bits are sent one after another over a single signal path, rather than simultaneously over many paths.

Given Data / Assumptions:

• We are discussing binary information transfer.
• Standard serial links (UART, SPI single-wire data line, I2C data line SDA, USB differential pair counted as a single logical channel) serialize bits in time.
• Physical layer specifics (electrical, optical, RF) may vary, but the logical idea remains: one channel carries the timed bit stream.

Concept / Approach:
Serial transmission sends data bit-by-bit in sequence across one communication path. This is contrasted with parallel transmission, where multiple conductors carry multiple bits at the same instant. Serial is favored for longer distances and high speeds because it reduces skew and cabling complexity.

Step-by-Step Solution:
1) Define serial: a single logical channel conveys a timed sequence of bits.2) Count conductors for the data path: one signal conductor (plus a reference/return path) is sufficient for data.3) Recognize that higher layers (protocol/encoding) do not change the single-channel nature of serial data.4) Conclude that the correct choice is the one identifying a single conductor for the signal path.

Verification / Alternative check:
Compare with parallel buses (older printer ports, address/data buses) which require many conductors. Serial standards (RS-232 TX line, 1-Wire, half-duplex UART) still send bits on one signal conductor, confirming the principle.

Why Other Options Are Wrong:
Multiple conductors: describes a parallel bus, not serial.Infrared only: serial is not limited to IR; it can be electrical, optical, or RF.Fiber-optic ribbon per bit: that is a parallel optical concept, not serial.

Common Pitfalls:
Confusing the presence of a ground/return conductor with “multiple conductors for data.” The question focuses on the data signal path count, not the necessary return/reference path.

Final Answer:
A single conductor