This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Input: Consider Input: Passage: Most migrations begin with the birds starting off in a broad front. Often, this front narrows into one or more preferred routes termed flyways. These routes typically follow mountain ranges or coastlines, sometimes rivers, and may take advantage of updrafts and other wind patterns or avoid geographical barriers such as large stretches of open water. The specific routes may be genetically programmed or learned to varying degrees. The routes taken on forward and return migration are often different. A common pattern in North America is clockwise migration, where birds flying North tend to be further West, and flying South tend to shift Eastwards. Question: What obsticals will migrating birds avoid?

Output: large stretches of open water

Input: Consider Input: Passage: In September 1993, Madonna embarked on The Girlie Show World Tour, in which she dressed as a whip-cracking dominatrix surrounded by topless dancers. In Puerto Rico she rubbed the island's flag between her legs on stage, resulting in outrage among the audience. In March 1994, she appeared as a guest on the Late Show with David Letterman, using profanity that required censorship on television, and handing Letterman a pair of her panties and asking him to smell it. The releases of her sexually explicit films, albums and book, and the aggressive appearance on Letterman all made critics question Madonna as a sexual renegade. Critics and fans reacted negatively, who commented that "she had gone too far" and that her career was over. Question: What was Madonna dressed in for the tour?

Output: whip-cracking dominatrix

Input: Consider Input: Passage: During the years 1940-1955, the rate of decline in the U.S. death rate accelerated from 2% per year to 8% per year, then returned to the historical rate of 2% per year. The dramatic decline in the immediate post-war years has been attributed to the rapid development of new treatments and vaccines for infectious disease that occurred during these years. Vaccine development continued to accelerate, with the most notable achievement of the period being Jonas Salk's 1954 development of the polio vaccine under the funding of the non-profit National Foundation for Infantile Paralysis. The vaccine process was never patented, but was instead given to pharmaceutical companies to manufacture as a low-cost generic. In 1960 Maurice Hilleman of Merck Sharp & Dohme identified the SV40 virus, which was later shown to cause tumors in many mammalian species. It was later determined that SV40 was present as a contaminant in polio vaccine lots that had been administered to 90% of the children in the United States. The contamination appears to have originated both in the original cell stock and in monkey tissue used for production. In 2004 the United States Cancer Institute announced that it had concluded that SV40 is not associated with cancer in people. Question: Who created the polio vaccine?
Output: Jonas Salk