The correct answer is '5 GHz'. This frequency band is less congested than the 2.4 GHz band and generally offers better performance in environments with many existing wireless networks. The 5 GHz band also supports a larger number of non-overlapping channels, which reduces the risk of interference. The other options, while they are valid frequency bands, would not be optimal. The 2.4 GHz is already noted as congested, and the technician is looking to avoid interference. The 6 GHz band is newer and may not be supported by all devices, which could limit connectivity.