A train stops at a station(车站). A young man wants to come out, but it is raining. A boy is standing under a big umbrella. The young man says to the boy，"Can you go and get us two hamburgers, one for you and one for me? Here are two dollars. " "Great！"says the boy and he goes to buy hamburgers. After some time, the boy is back. He is eating a hamburger. "Where is my hamburger？"asks the young man. "Oh, there is only one hamburger left(剩下). So I'm eating mine. Here is your dollar. "

19世纪后期，主要资本主义国家进入垄断阶段，“垄断”的本质是