This question tests your knowledge of inversion with negative adverbs and the correct tense sequence. The sentence begins with "Hardly," a negative adverb, which triggers subject-auxiliary inversion. Additionally, the phrase "Hardly...when" typically connects two past actions, where the first action (reaching the train) happened immediately before the second (the train started moving).
When a sentence begins with "Hardly," "Scarcely," or "No sooner," the auxiliary verb comes before the subject. The action that occurred first is usually in the past perfect tense (had + subject + past participle), followed by the simple past tense for the subsequent action. Here, reaching the train happened before it started moving.
- A: "I had reached" uses the correct past perfect tense but does not apply inversion, which is mandatory when "Hardly" starts the sentence.
- C: "I reached" uses the simple past tense and lacks inversion, making it incorrect for both tense and structure.
- D: "did I reach" uses the simple past tense with inversion. While inversion is present, the simple past doesn't accurately convey that reaching the train was an action completed *before* another past action, which the past perfect does.
Therefore, B: "had I reached" is the correct option, as it correctly applies both the inversion rule (auxiliary 'had' before subject 'I') and the past perfect tense, indicating the sequence of events.