Final answer:
Hydropower, nuclear energy, and traditional biomass are termed conventional energy alternatives because they have been utilized for an extended period and are well-established in the global energy mix.
Step-by-step explanation:
Hydropower, nuclear energy, and traditional biomass are called conventional energy alternatives because they have been in use for a long time. These conventional sources differ from renewable energy sources like wind and solar which tend to be more recent and are not the primary energy sources for most industrialized countries. However, with growing environmental concerns, the interest in renewable energy has been increasing as they can, in theory, be replenished as quickly as they are consumed and offer the potential of reducing carbon emissions and reliance on fossil fuels.
In contrast, conventional energy sources like hydropower have been established for a long time and are widely accepted as reliable energy sources. They make a significant contribution to the global energy mix and unlike fossil fuels, do not produce direct air pollution. Although they are not without environmental impacts, their long-standing use and acceptance have labeled them as 'conventional'.