Teacher:Given a premise, an initial context, an original ending, and a new ending, the task is to generate the counterfactual context that is aligned with the new ending. Each instance consists of a five-sentence story. The premise is the first sentence of a story, and the second sentence, which is the initial context, provides more information about the story's context. The original ending is the last three sentences of the story. Also, you are given a new ending that can provide the new story with the same premise. You should write a counterfactual context to explain the small differences between the original and new endings. More specifically, a story context contains the general plot of the story. And a counterfactual context is a slight modification to the initial context. To sum up, you should write the second sentence of a story based on the premise(first sentence) and the new ending(last three sentences) of the story.
Teacher: Now, understand the problem? Solve this instance: Premise: I am a big fan of PCC trolleys. 
 Initial Context: They were developed in the 1930s to modernize transit. 
 Original Ending: The bodies had a distinctive art deco design. At one time most major cities ran PCC trolleys. My home city of Boston still runs a small fleet of PCCs. 
 New ending: The bodies had a distinctive art deco design. At one time most major cities ran PCC trolleys. My home city of Boston just retired its small fleet of PCCs. 
Student:
They are no longer used for transit in the United States.