The correct answer is A. RJ11.

According to CompTIA A+ Core 1 220-1201 objectives under Networking:

RJ11 connectors are commonly used for telephone lines and data cables that use two pairs of wires (four wires total).

This connector is standard for analog telephone connections and DSL connections.

Why the other options are incorrect:

B. F-type: Used for coaxial cables, commonly in cable TV or broadband internet, not for two-pair data cables.

C. ST: A type of fiber optic connector, not used for copper two-pair wiring.

D. Molex: Primarily used for power connections in computer hardware, not for network or phone cabling.