The environmental benefits gained by using renewable resources among the options provided are:
A. Fewer greenhouse gases emitted - This is a significant advantage of renewable resources, as they typically produce little to no greenhouse gas emissions compared to fossil fuels.
B. Fewer migratory birds harmed by wind turbines - This statement can be somewhat misleading. While efforts are being made to minimize harm to birds, wind turbines can still pose risks to migratory birds. The impact varies by location and technology used, so this is not universally seen as an environmental benefit of renewable resources.
C. Open spaces can be used to construct solar farms - While utilizing open spaces for solar farms can be seen as a benefit in terms of land use efficiency, it's not explicitly an environmental benefit in the same sense as reducing emissions or preserving biodiversity.
Based on these interpretations, option A is a clear environmental benefit, while B and C have more nuanced implications.