Answer:
A. Yes, because chatting with others is not inherently part of buying groceries
Explanation:
When a third party benefits from the transaction between two parties its is known as economic transaction. For example when the parents pay for college education for their children, school and the parents are not the only beneficiaries , it is also beneficial for the society as the student would become a good citizen and that would solve many social problems itself.
Standing in line at small town grocery store gives the people chance to socialise. It is part of positive externality because chatting with others is not inherently part of buying groceries, it is an extra benefit for the buyers.