A company is experiencing network delays. The network administrator discovers that a worker in a location far from the MDF has connected an old 10BASE-T switch with redundant links to the existing network. How could this action be responsible for the impaired network performance?（）

• A、Connecting a host to the old switch has created a broadcast storm.
• B、The 10BASE-T switch forced the entire network to be reduced to 10 Mbps operation.
• C、The old switch does not support VLANs, which has disabled the VLAN configuration of the entire the network.
• D、The old switch does not support full-duplex operation, effectively forcing half-duplex operation throughout the network.
• E、Spanning Tree Protocol has elected the old switch as the root bridge, creating inefficient data paths through the switched network.