Final answer:
The most suitable search phrase for Janirah's research on the impact of the "Let's Move!" campaign on childhood obesity rates in Louisiana is A. Louisiana childhood obesity rates, as it combines both the location and demographic context.
Step-by-step explanation:
The best search phrase for Janirah to use in her research on how Michelle Obama's "Let's Move!" campaign has affected the obesity rate of children in Louisiana is: A. Louisiana childhood obesity rates. This particular search phrase targets both the geographical area of interest (Louisiana) and the specific demographic (childhood) related to the obesity rates that Janirah is researching. It is a more focused search term that is likely to yield specific results about changes in obesity rates among children in Louisiana since the launch of the Let's Move! campaign.
To better understand the context, Janirah could also look into search phrases like B. Let's move campaign and D. Michelle Obama Louisiana to gain more insight into the campaign's initiatives and their potential impact within the state. However, for a comprehensive understanding of the subject matter, including relevant statistics and any assessment of the campaign's effectiveness, the initial search phrase is most apt.