英语语法分析

Navajo is hard to learn and only a few people know it.

纳瓦霍语很难学，只有少数人知道。

They were called the Navajo code talkers.

他们被称为纳瓦霍密码员。

It was a spoken code, never written down, and it was developed and used by Navajo Indians.

这是一种从未被记录下来的口头密码，由印第安部落纳瓦霍人开发和使用。