Later, as Clinton's troops were heading up the Hudson Valley, Clinton used another device to pass the news of his whereabouts to Burgoyne. Clinton wrote a message on a piece of silk that he put in a silver ball about the size of a musket ball. (Clinton also sometimes cut a message into long, narrow strips and coiled them into the hollow quill of a large feather.) Clinton gave the silver ball to Daniel Taylor, a young officer, promising that Taylor would be promoted if he got the message to Burgoyne. If he were captured, he was to swallow the ball. Because it was made of silver, it could not harm him.

The author’s main purpose in this excerpt is to

persuade the reader that a spy named Daniel Taylor is a hero.
entertain the reader with a humorous story about a young officer.
prove that spying was the only way for the Americans to win the war.
give an example of creative spying during the American Revolution.