Answer: C) The Americans were persuaded to join the war against Germany after seeing the telegram.
Step-by-step explanation: In the given excerpt from "The Dark Game" we can see that the British home secretary, read a telegram send by Zimmerman and decided to present it to President Wilson, this action caused that a couple of months later, the United States declared war on Germany and its allies. So, based on the information in the excerpt we can infer that the Americans were persuaded to join the war against Germany after seeing the telegram.