Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
Paul Krugman replies to John Cassidy Letter from M. Mitchell Waldrop Paul Krugman replies to M. Mitchell Waldrop Letter from Kenneth J. Arrow Letter from Ted C. Fishman David Warsh's July 3, 1994, Boston Globe Letter from John Cassidy: Paul Krugman loves to berate journalists for their ignorance of economics, particularly his economics, but on this occasion, I fear, his logic is more addled than usual. I am reluctant to dignify his hatchet job with a lengthy reply, but some of his claims are so defamatory that they should be addressed, if only for the record. 5) For a man who takes his own cogitations extremely seriously, Krugman is remarkably cavalier about attributing motives and beliefs to others. "Cassidy has made it clear in earlier writing that he does not like mainstream economists, and he may have been overly eager to accept a story that puts them in a bad light," he pronounces. I presume this statement refers to a critical piece I wrote in 1996 about the direction that economic research, principally macroeconomic research, has taken over the past two decades. In response to that article, I received dozens of messages of appreciation from mainstream economists, including from two former presidents of the American Economic Association. Among the sources quoted in that piece were the then-chairman of the White House Council of Economic Advisers (Joseph Stiglitz), a governor of the Federal Reserve Board (Laurence Meyer), and a well-known Harvard professor (Gregory Mankiw). To claim, as Krugman does, that I "don't like mainstream economists" and that I am out to denigrate their work is malicious hogwash. The fact of the matter is that I spend much of my life reading the work of mainstream economists, speaking to them, and trying to find something they have written that might interest the general public. In my experience, most economists appreciate the attention. 6) I might attach more weight to Krugman's criticisms if I hadn't recently reread his informative 1994 book Peddling Prosperity , in which he devotes a chapter to the rediscovery of increasing returns by contemporary economists. Who are the first scholars Krugman mentions in his account? Paul David, an economic historian who wrote a famous paper about how the QWERTYUIOP typewriter keyboard evolved and, you guessed it, Brian Arthur. "Why QWERTYUIOP?" Krugman wrote. "In the early 1980s, Paul David and his Stanford colleague Brian Arthur asked that question, and quickly realized that it led them into surprisingly deep waters. ... What Paul David, Brian Arthur, and a growing number of other economists began to realize in the late seventies and early eighties was that stories like that of the typewriter keyboard are, in fact, pervasive in the economy." Evidently, Krugman felt four years ago that Arthur's contribution was important enough to merit a prominent mention in his book. Now, he dismisses the same work, saying it "didn't tell me anything that I didn't already know." Doubtless, this change in attitude on Krugman's part is unconnected to the fact that Arthur has started to receive some public recognition. The eminent MIT professor, whose early academic work received widespread media attention, is far too generous a scholar to succumb to such pettiness. --John Cassidy Paul Krugman replies to John Cassidy: I think that David Warsh's 1994 in the Boston                 Globe says it all. If other journalists would do as much homework as he did, I wouldn't have had to write that article. Letter from M. Mitchell Waldrop: c) So, when I received Krugman's letter shortly after Complexity came out, I was puzzled: He was complaining that I hadn't referenced others in the increasing-returns field--Paul Krugman among them--although I had explicitly done so. d) But, when I checked the published text, I was chagrined to discover that the critical passage mentioning Krugman wasn't there. e) Only then did I realize what had happened. After I had submitted the manuscript, my editor at Simon &amp Letter from Kenneth J. Arrow: Paul Krugman's attack on Brian Arthur ("The Legend of Arthur") requires a correction of its misrepresentations of fact. Arthur is a reputable and significant scholar whose work is indeed having influence in the field of industrial organization and in particular public policy toward antitrust policy in high-tech industries. Krugman admits that he wrote the article because he was "just pissed off," not a very good state for a judicious statement of facts, as his column shows. His theme is stated in his first paragraph: "Cassidy's article [in The New Yorker of Jan. 12] tells the story of how Stanford Professor Brian Arthur came up with the idea of increasing returns." Cassidy, however, said nothing of the sort. The concept of increasing returns is indeed very old, and Cassidy at no point attributed that idea to Arthur. Indeed, the phrase "increasing returns" appears just once in Cassidy's article and then merely to say that Arthur had used the term while others refer to network externalities. Further, Arthur has never made any such preposterous claim at any other time. On the contrary, his papers have fully cited the history of the field and made references to the previous papers, including those of Paul Krugman. (See Arthur's papers collected in the volume Increasing Returns and Path Dependence in the Economy, especially his preface and my foreword for longer comments on Arthur's work in historic perspective. Click to see the foreword.) Hence, Krugman's whole attack is directed at a statement made neither by Arthur nor by Cassidy. Krugman has not read Cassidy's piece with any care nor has he bothered to review what Arthur has in fact said. What Cassidy in fact did in his article was to trace a line of influence between one of Arthur's early articles and the current claims of the Department of Justice against Microsoft. It appears that Cassidy based his article on several interviews, not just one. --Kenneth J. Arrow Nobel laureate and Joan Kenney professor of economics emeritus Stanford University Letter from Ted C. Fishman: After reading Paul Krugman vent his spleen against fellow economist Brian Arthur in "The Legend of Arthur," I couldn't help wondering whose reputation he was out to trash, Arthur's or his own. Krugman seems to fear a plot to deny economists their intellectual due. If one exists, Arthur is not a likely suspect. In a series of long interviews with me a year ago (for Worth magazine), I tried, vainly, to get Arthur to tell me how his ideas about increasing returns have encouraged a new strain of economic investigations. Despite much prodding, Arthur obliged only by placing himself in a long line of theorists dating back to Adam Smith and Alfred Marshall. I also found him disarmingly generous in giving credit to the biologists, physicists, and fellow economists who have helped advance his own thinking. Savvy to the journalist's quest for heroes, Arthur urged me to focus on his ideas, not his rank among his peers. Krugman has made a career out of telling other economists to pay better attention to the facts, yet as a chronicler of Arthur's career and inner life, Krugman seems to have listened only to his own demons. --Ted C. Fishman (For additional background on the history of "increasing returns" and Brian Arthur's standing in the field, click for David Warsh's July 3, 1994,                                 Boston Globe                                    article on Brian Arthur)

<question>:
Which of the following most likely happened to Krugman after these letters?

<options>:
A Krugman wrote an official apology to the writers.
B Krugman wrote another book about increasing returns.
C Krugman quit writing in newspapers.
D Krugman lost credibility among his colleagues.

<answer>:

D