Answer:
The correct answer is C. 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.
Explanation:
The main idea of a text is always the central point the author wants to convey. In the case of the excerpt presented, this focuses on the role of interpreters at the Ellis Island, especially their role to support the communication of immigrants and natives of the island. This idea is developed through supporting details such as "strong linguistic skills" or "the equivalent (or a close equivalent) of the words and meanings". According to this, the main point is best expressed in the sentence "An interpreter needed to convey the equivalent..." because this sentence directly states the role and importance of interpreters at Ellis Island, which is the focus of the text.