Final answer:
The sentence in paragraph 2 that best refines the author's main claim about urban gardens is 'Most importantly, urban gardens help people have access to the healthy food they need.' The sentence that refines the main claim about urban gardens is the one emphasizing their role in providing access to healthy food.
Step-by-step explanation:
The sentence in paragraph 2 that best refines the author’s main claim about urban gardens is: “Most importantly, urban gardens help people have access to the healthy food they need.” This sentence directly supports the main claim by emphasizing the critical role of urban gardens in ensuring access to nutritious food, which is a fundamental aspect of fostering healthier communities. It aligns with the provided texts, which discuss the impact of urban gardens on food security, nutrition, community engagement, and the incorporation of immigrant populations into their new environments.