Shielded twisted-pair (STP) cable includes a conductive layer that provides a barrier to protect the data signals from external electromagnetic interference (EMI), making STP the correct choice in environments with high levels of interference. Unshielded twisted-pair (UTP) cable lacks this shielding, and while it is widely used due to its lower cost and easier handling, it is more susceptible to EMI. Flat Ethernet cable refers to the physical shape of the cable and does not inherently address interference issues. Coaxial cable, while resistant to EMI, is not typically used for modern Ethernet networks and would not be the appropriate choice for a network environment experiencing EMI issues on twisted-pair cable runs.