Step 1: Understanding the Use of 'Did':
"Did" is used in questions and negative sentences to form the past tense of a verb. In this case, "did" is used to indicate the past tense of "know."
Step 2: Analyzing the Options:
- Have: This is incorrect because "have" is used in present perfect sentences, not simple past.
- Ought: This is incorrect because "ought" suggests duty or obligation, which doesn't fit the context of the sentence.
- Might: This is incorrect because "might" suggests possibility and does not fit with the structure of the sentence.
- Did: This is the correct option, as it is used for simple past tense questions and statements.
Step 3: Conclusion:
The correct answer is did.