In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Article: The story happened during the Second World War. An old man lived in a small town of Germany. He had three sons and they all worked in the same factory where he had worked. After the war had begun, his sons were all made to join the army one after another and they all died in the fights. The old man was very sad. He didn't have enough food and was often hungry. And nobody helped him and he didn't know how to go on living. It was a very cold winter night. The old man couldn't go to sleep. He had been hungry for two days and it was so cold in his room that ice could be seen. He had to get up and began to run in the room until he lay down on the floor. The next morning he had to beg from door to door. He had been to a lot of cities and knew a lot. Once he came to a village, but the villagers were all poor and couldn't give him anything. He was too hungry to go to another village. He thought hard and found a way. He came to a police station and called out, "Hitler is a foolish pig!" Out came an old policeman at once. He took the old man into a room, gave him some bread and a cup of tea. Then he said, "Don't say so in our village, sir!" "I'm sorry, sir," said the old man. "I don't know it's Hitler's hometown." "No, no, sir," the policeman said in a hurry. "It's pigs' hometown!"
Answer: they had to do so
The old man's sons joined the army because _ .

Article: Scientists have proved that sleeping and learning go hand in hand. Even a short nap can boost our memory and sharpen our thinking. But the relationship goes deeper than that. "The brain is not passive while you sleep," scientist Anat Arzi said. "It's quite active. You can do many things while you are asleep." Arzi and her coworkers didn't try to teach the sleeping volunteers any complex information, like new words or facts. Instead, the scientists taught volunteers to make new connections between smells and sounds. When we smell something good, like a flower, we take deep breaths. When we smell something bad, we take short breaths. Arzi and her co-workers based their experiment on these reactions. Once the volunteers fell asleep in the lab, the scientists went to work. They gave them a whiff of something pleasant and meanwhile played a particular musical note. They didn't wake up, but they heard--and sniffed deeply. Then the scientists gave the volunteers a whiff of something terrible and played a different musical note. Again, the volunteers heard and smelled--a short snort this time--but didn't wake up. The researchers repeated the experiment. After just four repetitions, volunteers made a connection between the musical notes and their paired smells. When the scientists played the musical tone that went with good smells, the sleepers breathed deeply. And when the scientists played the musical tone that went with bad smells, the sleepers breathed briefly--despite there being no bad smell. The next day, the volunteers woke up with the sound-smell connection. They breathed deeply when hearing one tone and cut their breaths short when hearing the other, which must have been unusual for them. Imagine walking down the street and taking a deep breath upon hearing a particular sound!
Answer: to make sound-smell connections
In the study, the volunteers were taught _ .

Article: What is it: Work & Travel USA Who are qualified: Fulltime college students, above 18 years old About the program: Application for the 2009 Work & Travel USA program has just started. It's an 8~16 weeks' summer program for college students to work and travel in the U.S.. Employers include Boeing, Hilton Hotel and 7Eleven. For next summer, about 3,500 positions are open to Chinese students. Applicants must pass a language test and sometimes an interview, and pay a registration fee to join the program. (Source: www. Cultureexchange. org) _ What is it: Shanghai Volkswagen jobs Who are qualified: College students graduating in 2009 About it: Shanghai VW offers over 300 positions from engineering to marketing to college students graduating in 2009. Applicants should have an excellent academic record, CET6 or the same level language certificate in German, and good computer skills. Campus talks will take place in Shanghai, Changchun, Harbin, Wuhan, Changsha, Nanjing, Beijing and Xi'an from October. (source: campus chinahr. com/2009/pages/csvw) _ What is it: Oak Pacific Interactive (OPI) internships Who are qualified: College juniors and firstyear postgraduate students About it: OPI is now offering internship positions for test engineer, development engineer and assistant to the director of corporate culture. For engineering positions, candidates should major in computer science or a related field, have communication ability and be familiar with various development languages. For assistant to the director positions, candidates should be adept in document writing, activities organizing and office software. (source: campus. xiaonei. com)
Answer: on the Internet intended for college students to read
These advertisements are most probably advertisements _ .