Given the task definition and input, reply with output. Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.

How is er what are refineries often called?

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
What are refineries often called?