Final answer:
Farmers are most likely smiling because their crops have been successful, indicating a fruitful harvest season causing satisfaction and reason for celebration.
Step-by-step explanation:
Based on Wil's observations and provided reference materials, the farmers are MOST LIKELY smiling in the story because b) Their crops have been successful. The mentions of farmers looking forward to autumn and the association with peace and ease suggest that the hard work led to a fruitful harvest. Additionally, historical and cultural contexts indicate that the end of the harvest season is a time of social celebration and reflection on the success of crops, which would naturally elicit smiles from the farmers.