The correct answer is B.
A code talker was a person employed by the military during a wartime.
This person used a little known language as a way of communicating secret messages. Many Native Americans were code talkers during both wars, they communicated in their native languages in order to deceive the enemy spying on them.
Code talking was pioneered by the Cherokee and Choctaw tribes during World War I.
The bilingual people from the Navajo tribe were recruited during World War II by the US Marine Corps. They were serving in the standard communication units in the Pacific Theater.