完形填空。阅读下列短文，从短文后各题所给的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项。
Last Sunday, I sat with Tony, my college classmate, in a well-known coffee shop in Buenos Aires, Argentina. As we1our coffee, two men entered and sat on an empty table beside us.
They2the waiter and ordered three cups of 3, two on the table and one on the wall. We heard this order with great4and observed that they were served with two cups of coffee 5they paid for three. As soon as they6, the waiter pasted (粘贴) a piece of paper on the wall saying A Cup of Coffee.
It 7that the matter was normal at this place. However, it was something8for Tony and me. Since we had nothing to do with the matter, we 9our coffee, paid the bill and left.
After a few days, we again had a10to go to this coffee shop. While we were enjoying our coffee, a man entered. The way this man was dressed did not 11the standard nor the atmosphere of this coffee shop. Poverty was12from the looks on his face. As he13himself, he looked at the14and said, “One cup of coffee from the wall.” The waiter served coffee to this man with15, politeness and warmth.
After a few minutes, the man finished his coffee and left16paying. We were amazed to watch all this when the waiter 17a piece of paper from the wall and18it in the dustbin.
Now it was no 19for us because the matter was very clear. Although the man didn't know about the one who was giving this cup of coffee to him, he would have a better understanding of the wall which had a great role between the 20and receiver.
