Which group provided secure battlefield radio communication in the pacific theater in world war ii?

For the United States, the Navajo Code talkers provided secure battlefield radio communication in the pacific theater. This group of Native Americans were trained by the US military and helped in relaying important information during the middle of battle. The reason the Navajo Indians were picked were due to the complexity of their language. The American forces knew that other codes or languages they've used before could be easily intercepted by the Axis powers. To ensure this did not happen, the American military recruited the Navajo.

The answer is c. good luck : )