Direct: "Which platform does the night train use?" Reported after the old timetable ended: A traveller asked ___.
which platform the night train used✓Correct answer
which platform did the night train use
which platform does the night train use regularly
which platform did the night train used before departure
Explanation
Which platform the night train used correctly combines the retained wh-phrase with statement order. Which platform did the night train use wrongly leaves do-support in a reported question.