Answer:
The research question that is most effective depends on the context and purpose of the research, but in general, B. How did natural gas affect the ozone layer in 1975? is more effective than the other options as it is specific, focused and clearly states the subject matter and the time period in question.
It is also a research question that could lead to a more nuanced and detailed understanding of the environmental impact of natural gas during that specific year, which could have important implications for current environmental policy and decision-making.
Option A. What are fossil fuels? is too broad and basic, while option C. How do fossil fuels affect the atmosphere? is too general and lacks specificity, making it difficult to know where to focus the research. Option D. When were fossil fuels first discovered? is a historical question and not related to the environmental impact of fossil fuels.