What is the correct way to complete the sentence: What ____ (you, do) at 7 o'clock yesterday?

The correct way to complete the sentence is: What **did** you do at 7 o'clock yesterday? **Explanation:** 1. **Identify the tense:** The question is about an action that happened in the past ('yesterday'), so we need to use the past simple tense. 2. **Form the past simple question:** To form a question in the past simple tense with 'you', we use the auxiliary verb 'did' before the subject and the base form of the main verb ('do'). 3. **Complete the sentence:** Therefore, the missing word is 'did'. The completed sentence is 'What did you do at 7 o'clock yesterday?'