It is likely that increased global temperatures (Option D) would have the greatest impact on reducing water resources that could be used for energy production. This is because, as temperatures rise, there is an increased likelihood of water scarcity due to decreased precipitation and increased evaporation. This can lead to a reduction in the availability of water for hydroelectric power generation, irrigation for biofuel crops, and cooling for thermal power plants.
Option A, increased pollution, can also have an effect on the availability of water resources for energy production, as pollution can make water sources unsafe for human consumption and power generation. However, the impact of pollution on water resources is likely to be less significant than the impact of increased temperatures.
Option B, increased deforestation, can also affect water resources, as trees play a crucial role in maintaining the water cycle by absorbing and releasing water vapor. Deforestation can lead to a reduction in precipitation and an increase in surface runoff, which can make water less available for energy production.
Option C, increased human population, can also have an impact on water resources, as a larger population can lead to increased demand for water for domestic, industrial and agricultural use. This can lead to over-extraction of water resources, which can reduce the availability of water for energy production. However, the impact of population growth on water resources is likely to be less significant than the impact of increased temperatures.
In summary, while all of the listed options can have an impact on reducing water resources that could be used for energy production, it is likely that increased global temperatures would have the greatest impact as it affects the entire water cycle, making water less available for energy production.