Returns to scale is a concept that operates Naim 21:34 Microeconomic Theory Chapter 6 Returns to scale is a concept that operates A) only in the short run. B) only in the long run. C) in both the long run and the short run. D) in either the long run or the short run but never both. Answer: only in the long run. Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+