Language is sometimes written as a code so that people can communicate secrets. During     1     Second World War, the German Navy （海军）used a code to send messages. The British broke the code and     2     （learn） about many German plans. The Japanese also used a code to talk to     3     （they） ships at sea. It was called the Purple Code. Although the Americans soon broke this code, the Japanese didn’t know it     4    （break）. In 1942 , the Americans began to use their own code to send     5     （secret）. A few Navajo（纳瓦在人）Indians made this code     6    （base） on their language, which only some American Indians spoke. The code described a few things the American army did. Only they could understand this code, so they went with the army as it fought against the Japanese. These Navajo soldiers promised     7    （keep） this code a secret, even though this could cause their     8    （die）. The Japanese never broke the code because they knew nothing     9     the Navajo language. And the code,     10     connected two languages, helped win the war in the Pacific.