Final answer:
The correct word to complete the sentence is 'arrives', making the full sentence, 'My train arrives in Philadelphia at noon.'
Step-by-step explanation:
The sentence "My train _____ in Philadelphia at noon." requires the correct form of a verb that matches the subject 'My train' to express an action or state of being. The sentence is discussing an event happening at a specific time, which is the arrival of a train, so an appropriate verb to complete this sentence would be 'arrives'. Therefore, the completed sentence should read: "My train arrives in Philadelphia at noon." This statement indicates that the train is scheduled to reach Philadelphia right when the clock hits noon.