【内容提示】
根据下面的内容提示写一篇因果分析型文章：
纽约城市旅客社（The New York City Visitor"s Bureau）说， 50年前首先把纽约叫成“大苹果”的是爵士乐手和其他文娱表演人员。那时，他们每天转场到一个城镇。他们把每一个城镇称做树上的一颗苹果。一个演员不能在纽约获得成功，就不能看做是成功演员。这样，他们就把纽约叫做“大苹果”了。
【作文示范】
Why New York Is Called the Big Apple
The New York City Visitor"s Bureau says jazz musicians①and other entertainers② first called New York the Big Apple fifty years ago。
At that time jazz musicians earned money by performing in many cities and towns across the United States。 They usually played their music in a different town each night。 But the performers would like to play in New York City best of all。 New York was the place with the best-paid jobs， the most money to earn， and a greater number of people for jazz music。 A performer was not considered successful until he was successful in New York。 The early jazz musicians described each town and city in America as an apple on a tree。 Naturally they called New York City the Big Apple。 Later a night club was named The Big Apple， and a popular dance was also called The Big Apple。 But no one except jazz musicians and some entertainers used this term to describe New York City。
About fifteen years ago， the city officials wanted to get more people to visit New York。 They needed a new symbol for their city。 They remembered the stories of the jazz musicians and began using the Big Apple in their advertisements。 The idea worked。
Today so many persons from different parts of the world come and visit New York City every day。 They may probably know New York"s nickname③， though they may not know why the city is called the Big Apple。