Examination analysis: examining tenses. I first met Lisa three years ago, when she was working in a clothing store. When we first met, she worked in a clothing store, which means that she did something at some point in the past, so she used the past continuous tense. Therefore, B is correct.

Comments: The key word of this question is at that time, which means that something is happening in the past time we just met, so we use the past continuous tense.