To identify the correct sentence structure, we should focus on the correct usage of "scarcely...when" which is a common correlative conjunction used in English to show one event that happened almost immediately after another:
- Examine the meaning of the sentence:
The sentence describes two events: 1) She reached the station, and 2) The train left. This suggests that the events followed each other in immediate succession.
- Understand the correct conjunction:
"Scarcely" is used with "when," not "than." "Than" is typically used for comparisons, thus incorrect in this structure.
- Consider grammatical structure:
The sentence must follow the structure "Scarcely had [subject] [past participle]... when [simple past]."
Apply these rules to the given options:
- Option 1: Scarcely had she reached the station when the train was leaving.
Though "when" is correct, the verb tense "was leaving" does not match the immediate action suggested by "scarcely." It should be in simple past tense.
- Option 2: Scarcely had she reached the station than the train was leaving.
Using "than" is incorrect for this structure.
- Option 3: Scarcely she had reached the station when the train left.
The word order is incorrect; it should be "Scarcely had she reached" for proper inversion.
- Option 4: Scarcely had she reached the station when the train left.
This follows the correct structure "Scarcely had [she] [reached]... when [the train left]."
Conclusion: Based on the rules of structure and correct use of conjunctions, the correct sentence is:
Scarcely had she reached the station when the train left.