Final answer:
Without additional context about Anna and Piper, it's not possible to specify which train they took. The options given, Orient Express, Trans-Siberian Railway, Eurostar, and Bullet Train, are all names of famous train routes.
Step-by-step explanation:
Unfortunately, with the information given in the question, it's not possible to determine what specific train Anna and Piper embarked on. The options provided are the names of famous train routes: Orient Express, Trans-Siberian Railway, Eurostar, and the Bullet Train. Without further specific context about the story or the characters, an accurate answer cannot be given.
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