The code is in the voice of a Native American. The man you just heard is singing a simple song in the Navajo language. Very few people outside the Navajo nation are able to speak any of their very difficult language.

　　At the beginning of World WarⅡ, the United States Marine Corps asked members of the Navajo tribe to train as Code Talkers.

　　The Cryptologic Museum says the Marine Corps Code Talkers could take a sentence in English and change it into their language in about 20 seconds. A code machine needed about 30 minutes to do the same work.

　　The Navajo Code Talkers took part in every battle the Marines entered in the Pacific during World WarⅡ. The Japanese were very skilled at breaking codes. But they were never able to understand any of what they called “The Marine Code. ”

　　The Cryptologic Museum has many pieces of mechanical and electric equipment used to change words into code. It also has almost as many examples of machines used to try to change code back into useful words.

　　【文章大意】2017年国家密码博物馆庆祝其60年卓越的密码逻辑, 这个事件标志着国家安全局成立了60周年, 两位前国家安全局员工分享了他们操作名叫Sigaba密码机的记忆。

　　1. The NSA was founded ________ .

　　A. in 1940

　　B. 1942

　　C. in 1952

　　D. in 2017

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