Which question may be used to start your initial research about "Global Warming"? a. How do you spell "global warming"? c. When did global warming first become a concern? b. Who is Al Gore? d. None of these

i think the question that may be used to start your initial research about global warming is : C. when did global warming first became a concern. A research should always started with a question and the research would be a set of events that carried out to find out the answer of that questions.