Passage 1 Questions 1 to 5 are based on the following passage 　Recently a new postage stamp has been issued to honor Flannery O'Connor and her great contributions to American Literature. The stamp costs 93 cents and has a pretty picture of the writer herself on it. She wears a top with a jewel neckline, and pearls. Her pink porcelain face, framed in a 1940s hairstyle, glows with the barest hint of a how-do-you do smile. 　This stamp does not, to my eyes, show Flannery O'Connor, the 20th-century of the short story, the "hermit（隐士） novelist" who fused her art and life as a Southerner and a Roman Catholic with stories that are shocking, hilarious （令人发笑的） and often bloody, the one who lived with her mother in Georgia and raised pheasants（雏鸡）， who got sick and died young in l9, who gazed at the sin-stricken world through cat-eye glasses that are as much as her visual signature as Hemingway’s beard or Frida’s eyebrow. 　This stamp shows the artist as a very young woman，barely 20 years old. It’s based on a photo of her as an undergraduate at Georgia State College for Women. Her works then amounted to cartoons and stories for the college magazine. 　The United States Postal Service gave this job to an art director, who lured a freelance artist. I spoke with both of them, and learned that neither knew much about O'Connor, but they did their best with the images they had. The artist told me he had read one of her novels in college. He knew O'Connor had raised pheasants, so he framed her with feathers. The art director remembered that her work was 'unsettling," and that she was a Catholic. 　I can't blame either of them for deciding on this striking portrait as the best fit for their tiny canvas, but I wish they and the Postal Service had produced a stamp that was more recognizably the grown-up Flannery, and contained some taste of her strange and noble artistic vision. 　I know she does not present an automatic illustrative equation, like mustache+ steamboat = Mark Twain. But a better choice would be a painting made by the author herself, a self-portrait from 1953. She is wearing a yellow straw hat,holding a devilish-looking pheasant and looking straight at you, harmful and brilliant, as if she could smell your stupidity. It is gorgeous and rough and honest and perfect.What does the phrase "an automatic illustrative equation" refer to?