The choice that would have the smallest impact on climate change when purchasing apples at the store is likely "buying apples in large quantities to reduce trips to the store." While reducing trips can save on transportation emissions, it does not directly address other significant factors like farming practices, packaging waste, and transportation emissions related to how far the apples have traveled from their source.
On the other hand, buying locally grown apples, supporting organic practices, and reducing packaging can have more direct benefits on reducing overall environmental impact and climate change.