Final answer:
The correct question tag for the sentence 'You came by the school bus' would be 'didn't you?'.
Step-by-step explanation:
Question tags are short questions that are added to the end of a statement to confirm information or seek agreement. They are usually composed of a helping verb and a pronoun that reflects the subject of the statement. In this case, the subject is 'you' and the helping verb is 'did'. Since the main statement is in the affirmative form ('You came by the school bus'), the question tag must be in the negative form ('didn't').
To complete this with the correct question tag, we should look at the structure of the main sentence. Because the main sentence is affirmative, the question tag needs to be negative. The correct completion using the verb 'did' to match the past simple tense and the pronoun 'you' would be 'didn't you?' Thus, the complete sentence with the correct question tag is: 'You came by the school bus, didn't you?'. Therefore, the complete sentence with the correct question tag would be: 'You came by the school bus, didn't you?'