Hubs operate in half-duplex mode and are limited to low speeds like 10Mbps, making them the most likely cause for the network card's performance issue. * Why Not A (DSL): DSL relates to internet connectivity, not local network hardware. * Why Not B (Unmanaged switch): Unmanaged switches typically support full-duplex and higher speeds than 10Mbps. * Why Not C (NIC teaming): NIC teaming increases bandwidth and redundancy, and is not relevant to this issue. CompTIA A+ Exam Reference: Core 1 (220-1101), Section 2.2, networking hardware.