Note: Depending on the context, the verb โexplotarโ can mean โto exploitโ or โto explodeโ. The imperfect is used in this context, because: The sentence is a description of an action in the past, i.e., the continuous exploding of the popcorn. The stem of the verb "explotar" is "explot-", formed by removing the final "ar". The third-person plural form "ellos/-as" (they) takes the conjugation suffix "-aban", i.e. "explotaban".
Note: Depending on the context, the verb โexplotarโ can mean โto exploitโ or โto explodeโ. The imperfect is used in this context, because: The sentence is a description of an action in the past, i.e., the continuous exploding of the popcorn. The stem of the verb "explotar" is "explot-", formed by removing the final "ar". The third-person plural form "ellos/-as" (they) takes the conjugation suffix "-aban", i.e. "explotaban".