What is the tense of the underlined verb in the sentence?

We had just begun to practice the skit when the fire alarm rang. A. past B. future perfect C. present perfect D. past perfect had and begun is underlined

D. past perfect

The tense of the underlined verb in the sentence: We had just begun to practice the skit when the fire alarm rang is past perfect. Notice the conditioning word "when" which dictates the sentence to be in the past perfect state in its action verb. Hence, "had" is added next to the past participle of the sentence. For example, the boy had played when suddenly his mom came.