This is VOA. The National Cryptologic Museum is on Fort George G. Meade, a military base near Washington, DC. The method of hiding exact meanings is called coding. People have used secret codes throughout history to protect important information. The National Cryptologic Museum celebrated 60 years of cryptologic excellence in 2012. One event there marked the sixtieth anniversary of the National Security Agency. Two former NSA workers shared their memories of operating a code machine called Sigaba.
In 1940, an American woman named Genevieve Grotjan found some information being repeated in Japanese coded messages. Her discovery helped the United States understand secret Japanese diplomatic messages. After the United States understood the code, it was possible to study messages from the Japanese ambassador to Germany and to his supervisors in Japan.
Understanding these messages helped the United States prepare for a possible war in the Pacific with Japan. After the attack on Pearl Harbor. the American naval commander in the Pacific Ocean was Chester Nimitz. His forces were much smaller than the Japanese Naval forces. And the Japanese had been winning many victories. Joseph Rochefort had worked for several months to read the secret Japanese Naval code called JN-25. If he could understand enough of the code, he would be able to give Admiral Nimitz very valuable information.
From the beginning of 1942, the Japanese code discussed a place called "AF." Joseph Rochefort felt the Japanese were planning an important battle aimed at "AF." After several weeks, he and other naval experts told Admiral Nimitz that their best idea was that the "AF" in the Japanese code was the American-held island of Midway. Admiral Nimitz said he must have more information to prepare for such an attack.
The Navy experts decided to trick Japan. They told the American military force on Midway to broadcast a false message. The message would say the island was having problems with its water-processing equipment. The message asked that fresh water be sent to the island immediately. This message was not sent in code.
Several days later, a Japanese radio broadcast in the JN-25 code said that "AF" had little water. Joseph Rochefort had the evidence he needed. "AF" was now known to be the island of Midway. He also told Admiral Nimitz the Japanese would attack Midway on June 13.The battle that followed was a huge American victory.  That victory was possible because Joseph Rochefort learned to read enough of the Japanese code to discover the meaning of the letters "AF."
One American code has never been broken. Perhaps it never will. It was used in the Pacific during World War Two. For many years the government would not discuss this secret code. Listen for a moment to this very unusual code. Then you may understand why the Japanese military forces were never able to understand any of it.
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 War Two, 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 War Two. 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.
The NSA was founded__________.

A．in 1940	B．1942
C．in 1952	D．in 2012

According to the passage, which one is not right?

A．“Cryptologic’’ implies containing some hidden information

B．The US decoded “AF” and won the victory in Midway Islands

C．Both Rchefort and Nimitz were American navy commanders

D．The US Marine Corps was fallen for in Midway Islands battle

The Americans used the Navajo language in their coding system during the Second World War for the reason that      .

A． unusual language was successfully used for codes

B．it was commonly used in coding system worldwide

C．the United States Marine Corps invented it then

D．it was the most beautiful language in the world

This passage is probably adapted from ____________.

A．an evening paper

B．a science fiction

C．a broadcasting program

D．a travel guidebook