If the writer were to delete the preceding sentence ("He knew that the Navajo language was very complex, had no written component, and that it was only spoken by people of Navajo origin."), the paragraph would primarily lose:
B An indication of the potential of the Navajo language.
This is because the deleted sentence provides context about the uniqueness and complexity of the Navajo language, which supports the idea that it would be an effective code for military communications. Without this context, the statement about it being "the perfect code" lacks the necessary background that underscores why the language's characteristics were advantageous for creating a code.