Read the excerpt from tools of the spymaster which statement best expresses the central idea of the excerpt

- Major Tallmadge developed a unique code system so that the Americans could send secret messages.

Explanation:

The above statement most appropriately communicates the controlling idea of the given excerpt that 'Major Tallmadge has advanced a unique code system for writing that would allow Americans to send secret messages.' This newly developed system of writing 'substituted digits for words and for words without number, he gave cipher' that assisted in keeping the content of the messages secret and maintain high-level security during the American Revolution. He describes the method of 'creative spying used during the revolution.'