Definition: used before nouns when only one of something exists Level: A1
你见过埃菲尔铁塔吗？
Have you seen ___the Eiffel Tower?
未来会发生什么？
What will happen in ___the future?
埃德·科赫曾多年担任纽约市市长。
Ed Koch was for many years ___the mayor of New York.
