Which of the following FCAW wires is designed to be either self-shielded or gas-shielded?

The choice of E492T-5 is correct because it is specifically designed as a flux-cored arc welding (FCAW) wire that can be utilized in both self-shielded and gas-shielded modes. This flexibility allows welders to adapt their welding techniques based on the specific requirements of the job or environmental conditions.

Self-shielded wires contain a core with a flux that generates shielding gases as the wire is consumed, making it ideal for outdoor conditions where wind may disperse traditional shielding gases. Gas-shielded wires, on the other hand, require an external shielding gas to protect the molten weld pool from atmospheric contamination, often providing better weld quality and control.

The other choices represent different types of FCAW wires that are not specified for dual shielding capability. For instance, E491T-7 focuses on specific applications and typically requires gas shielding for optimal results, while E492T-2 might not have the versatility that E492T-5 offers, hence they do not meet the criteria specified in the question.