Which sentence indicates that a past event was in progress when it was interrupted? a) rockwell had painted in his studio when a fire broke out and destroyed everything. b) rockwell was painting in his studio when a fire broke out and destroyed everything. c) rockwell painted in his studio when a fire broke out and destroyed everything. d) rockwell had been painting in his studio when a fire broke out and destroyed everything.

The answer is D) Rockwell had been painting in his studio when a fire broke out and destroyed everything.

Here, "had been painting" suggests that Rockwell was in the middle of painting in the studio when the fire started.

The correct answer is D) Rockwell had been painting in his studio when a fire broke out and destroyed everything

The verb form "had been painting" denotes an action that had happened in the past before another action in the past because it's a past perfect continuous tense. "fire broke out" uses past simple because it denotes an action that happened in the past, after the previous act of painting. This is why the sentence shows an action that happened but was interrupted by a latter action.