Single-mode fiber uses a beam of light to transmit data over long distances through a very thin, flexible cable. It is commonly used for high-speed data transmission across wide areas, such as between buildings or over long distances within a network. Single-mode fiber offers a higher bandwidth and longer distance capabilities compared to other types of fiber optics.

D. Single-mode fiber: Transmits data using light through a fiber optic cable, making it ideal for long-distance communication.

Why the other options are incorrect:

A. Coaxial: Coaxial cables use electrical signals, not light, to transmit data.

B. HDMI: HDMI (High-Definition Multimedia Interface) is used for transmitting audio and video signals but does not use light for data transmission.

C. Thunderbolt: Thunderbolt cables transmit data using electrical signals and are typically used for high-speed data transfer and display connections.

This falls under the Networking and Hardware domain in the CompTIA A+ Core 1 exam​.