Which of the following connector is used by Unshielded Twisted Pair (UTP)?

Concept: Physical-layer cabling standards pair a specific cable type with a specific connector shape and pin layout. For twisted-pair copper networking cable, the TIA/EIA-568 standard specifies an 8-position, 8-contact (8P8C) modular connector, popularly known as RJ45; a cable and connector are compatible only when both belong to the same standard family.

Application: Unshielded Twisted Pair (UTP) Ethernet cable is terminated at both ends with an RJ45 connector, which clips into the RJ45 port on network devices (switches, routers, NICs) and carries all eight conductors of the cable for Ethernet signaling. So, among the options given, RJ45 is the connector used with UTP cable.

Why the other jacks don't fit:

• RJ55 is not a defined designation in the Registered Jack series used for telecom/LAN cabling; no such standard connector exists, so it is never found on networking equipment.

• RS45 borrows the naming pattern of the EIA RS-series serial-interface standards (RS-232, RS-422, RS-485), which define point-to-point serial data links, not network cabling connectors. “RS45” itself does not correspond to any defined interface at all.

• RS55 has the same problem as RS45 — it mimics the RS-series serial-standard naming convention rather than naming an actual physical connector, and even genuine RS-standards are not used to terminate twisted-pair network cable.