Question

One 'code' that the Americans used to communicate during WWII was the

tank code

Navajo code

Hawaiian code

Answer 1

The Navajo code, which was not really a new code, was used during WWII. 
The Navajo code could not be deciphered because it wasn't a code at all it was the native language of the Navajo.

Answer 2

Answer:

navajo code

Explanation:

the navajo code was important diring WWII