Answer: A. A government website with data on air pollution throughout the United States
Step-by-step explanation:
From the question, we are informed that Francine is researching air pollution in major US cities and that she wants a source that would most likely support her research on air pollution in major US cities.
The source would be a government website with data on air pollution throughout the United States. This will help give the detailed information and data regarding air pollution in each states. This will be of immense benefit to the research in air pollution that Francine is doing.