Answer: The correct answer is C: decreased use of fossil fuels.
Explanation: The burning of fossil fuels causes the release of CO2 and other harmful substances into the atmosphere. Fossil fuels are fuels that are burnt by power plants and such to generate power. 
 
        
             
        
        
        
To determine if your hypothesis was correct for future reference
        
             
        
        
        
What was the investigation? But from my best guess I'm assuming it's the second option. This may be incorrect.
 
        
             
        
        
        
Answer:
The correct answer would be - observational approach.
Explanation:
Observation approach is the research technique that involves the observation  of the subject or participates behavior in their natural habitat or state. This will be one of best approach to study.
Similarly when characterizing new findings various aspect of  experimental, Observational details or modelling approaches will help in identification , classification and nomenclature. However, in comparison to experimental and modeling approach is more appropriate method for the rare endangered species.
Thus, the correct answer would be - observational approach.
 
        
             
        
        
        
Answer:
Limiting human use of nitrogen that is in the atmosphere.
Explanation: