The question is focused on the understanding of English tenses. The correct answer is 'B. Past Continuous' because this tense is used to describe an action that was ongoing at a particular moment in the past. Option A is incorrect because the Present Perfect tense is used for past actions with present relevance. Option C is incorrect because the Future Perfect tense is used for actions that will be completed by a certain time in the future. Option D is incorrect because the Present Continuous tense is used for actions that are currently ongoing.