Read the paragraph from "The Workers of Ellis Island." Interpreters translated for immigrants who could not communicate in English. Interpreters not only needed strong linguistic skills in one or more foreign languages, but they also needed to understand the most common dialects in a given language. An interpreter needed to convey the equivalent (or a close equivalent) of the words and meanings expressed by an alien immigrant and a United States Immigrant Inspector or other Ellis Island worker. Many interpreters at Ellis Island were either immigrants themselves or the children of immigrants.

Which sentence best represents the paragraph's central idea?

Interpreters translated for immigrants who could not communicate in English.
Interpreters not only needed strong linguistic skills in one or more foreign languages, but they also needed to understand the most common dialects in a given language.
An interpreter needed to convey the equivalent (or a close equivalent) of the words and meanings expressed by an alien immigrant and a United States Immigrant Inspector or other Ellis Island worker.
Many interpreters at Ellis Island were either immigrants themselves or the children of immigrants.