Which of the following Internet connection types is a digital form that runs over standard telephone wiring?

Fiber optic internet transmits data as pulses of light through glass or plastic fiber cables, not over standard copper telephone wiring.

Dial-up is an analog technology that modulates data as audible tones over the telephone voice band, meaning it is analog rather than digital and it occupies the phone line during use.

Cable internet uses coaxial cable originally built for cable television distribution, not standard telephone copper wiring.

DSL transmits digital data over the same copper twisted-pair telephone lines used for POTS by modulating high-frequency signals that do not interfere with voice, using a DSL filter or splitter to separate the two signals - this makes it a digital technology that runs over standard telephone infrastructure without requiring new cabling.