What is the question tag that can be added to the following sentence?
I used to swim in the Tilak tank.
This is question from an MCQ test whose options were
- did I?
- would I?
I agree with Barrie England's answer. I am only going to explain why the correct question tag for the given statement is didn't I?
In the sentence "I used to swim in the Tilak tank", used to is not functioning as an auxiliary verb because to goes with the verb swim making it an infinitive leaving used as the only finite verb in the sentence. Hence there is a need for an auxiliary verb and did is required in this case since used is in the past tense.
And because the statement is affirmative, the question tag should be negative. That's how didn't I? becomes the correct question tag.
For more on question tags, please refer to the link provided by tchrist in the comments above. It's a good one.