Answer: The correct answer is 4, to emphasize a clear similarity between the Gleasons and the Lins.
Explanation: The author first describes the shallow details of the dinner party: the food, the obvious details, etc. If you don't go deeper, you'll think it is about the differences. But then, he makes the point that serving dinner for your guests is the same in both families regardless of what they serve, just to do your best and hope for it t go that way too. Therefore, the author emphasizes on the similarities among two different cultures of the feeling when eating with friends and not properly on the food or habits.