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

<passage>:
Where it all started: Paul Krugman's                 "The Legend of Arthur." 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. 1) Krugman claims that my opening sentence--"In a way, Bill Gates's current troubles with the Justice Department grew out of an economics seminar that took place thirteen years ago, at Harvard's John F. Kennedy School of Government"--is "pure fiction." Perhaps so, but in that case somebody should tell this to Joel Klein, the assistant attorney general in charge of the antitrust division. When I interviewed Klein for my piece about the Microsoft case, he singled out Brian Arthur as the economist who has most influenced his thinking about the way in which high-technology markets operate. It was Klein's words, not those of Arthur, that prompted me to use Arthur in the lead of the story. 2) Krugman wrote: "Cassidy's article tells the story of how Stanford Professor Brian Arthur came up with the idea of increasing returns." I wrote no such thing, and Arthur has never, to my knowledge, claimed any such thing. The notion of increasing returns has been around since Adam Smith, and it was written about at length by Alfred Marshall in 1890. What I did say in my article was that increasing returns was largely ignored by mainstream economists for much of the postwar era, a claim that simply isn't controversial. (As Krugman notes, one reason for this was technical, not ideological. Allowing for the possibility of increasing returns tends to rob economic models of two properties that economists cherish: simplicity and determinism. As long ago as 1939, Sir John Hicks, one of the founders of modern economics, noted that increasing returns, if tolerated, could lead to the "wreckage" of a large part of economic theory.) 3) Pace Krugman, I also did not claim that Arthur bears principal responsibility for the rediscovery of increasing returns by economists in the 1970s and 1980s. As Krugman notes, several scholars (himself included) who were working in the fields of game theory and international trade published articles incorporating increasing returns before Arthur did. My claim was simply that Arthur applied increasing returns to high-technology markets, and that his work influenced how other economists and government officials think about these markets. Krugman apart, virtually every economist I have spoken to, including Daniel Rubinfeld, a former Berkeley professor who is now the chief economist at the Justice Department's antitrust division, told me this was the case. (Rubinfeld also mentioned several other economists who did influential work, and I cited three of them in the article.) 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: Thanks to Paul Krugman for his lament about credulous reporters who refuse to let facts stand in the way of a good story ("The Legend of Arthur"). As a professional journalist, I found his points well taken--even when he cites my own book, Complexity as a classic example of the gullibility genre. Among many other things, Complexity tells the story of the Irish-born economist Brian Arthur and how he came to champion a principle known as "increasing returns." The recent New Yorker article explains how that principle has since become the intellectual foundation of the Clinton administration's antitrust case against Microsoft. Krugman's complaint is that the popular press--including Complexity and The New Yorker --is now hailing Brian Arthur as the originator of increasing returns, even though Krugman and many others had worked on the idea long before Arthur did. I leave it for others to decide whether I was too gullible in writing Complexity . For the record, however, I would like to inject a few facts into Krugman's story, which he summarizes nicely in the final paragraph: Now, I will admit to many sins, not the least of them being a profound ignorance of graduate-level economics I spent my graduate-school career in the physics department instead, writing a Ph.D. dissertation on the quantum-field theory of elementary particle collisions at relativistic energies. However, I am not so ignorant of the canons of journalism (and of common sense) that I would take a plausible fellow like Brian Arthur at face value without checking up on him. During my research for Complexity I spoke to a number of economists about his work, including Nobel laureate Kenneth Arrow, co-creator of the General Equilibrium Theory of economics that Brian so eloquently criticizes. They generally agreed that Brian was a maverick in the field--and perhaps a bit too much in love with his own self-image as a misunderstood outsider--but basically sound. None of them warned me that he was usurping credit where credit was not due. Which brings me to Professor Krugman's letter, and my reply. I remember the exchange very well. Obviously, however, my reply failed to make clear what I was really trying to say. So I'll try again: a) During our interviews, Brian went out of his way to impress upon me that many other economists had done work in increasing returns--Paul Krugman among them. He was anxious that they be given due credit in anything I wrote. So was I. --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.

<question>:
What is the educational background of the person who wrote “Complexity”?

<options>:
A Law
B Economics
C Journalism
D Physics

<answer>:

D