Answer:
The passage in question is not provided, so I cannot reference specific evidence from it. However, based on historical context, it is possible to infer that the British waited until they were sure the telegram would encourage the US to enter the war.
One piece of evidence that supports this inference is the fact that the British intercepted the Zimmerman Telegram and held onto it for several weeks before sharing it with the United States. This delay suggests that they were strategic in their timing and wanted to ensure that the US would be more likely to enter the war if they were presented with the information at the right moment.
Another piece of evidence is the fact that the British had been trying to persuade the US to enter the war for some time. They had been sending messages and information to the US government in an effort to build support for their cause. It is reasonable to assume that they would have waited until they had a message that was particularly persuasive before sharing it with the US government.
Overall, these pieces of evidence suggest that the British were deliberate and strategic in their decision to share the Zimmerman Telegram with the US. They likely waited until they were confident that the message would have the desired effect before sharing it, which ultimately led to the US entering the war on the side of the Allies.