What type of solder should be used when a technician solders a spade connector to a wire?

The appropriate type of solder to use when soldering a spade connector to a wire is rosin core solder. This type of solder is designed with a flux core that aids in the soldering process by preventing oxidation and ensuring a strong electrical connection. The rosin acts as a cleaning agent that helps to prepare the metal surfaces for soldering, resulting in better adhesion of the solder to both the spade connector and the wire.

Using rosin core solder is particularly advantageous because it is easy to work with and provides a clean joint without excessive buildup of residues, which is essential in electrical applications. The other types of solder mentioned, while they may have specific applications, do not provide the same benefits for this scenario as they might not include the protective flux or may not be designed for electrical use.