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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.
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Article: A machine which makes water out of air could become the greatest household invention since the microwave. Using the same technology as a dehumidifier , the Water Mill is able to create a ready supply of drinking water by getting it from a limitless source-the air. The company behind the machine says not only does it offer all alterative to bottled water in developed countries,but it is a solution for the millions who face a daily water shortage. The machine works by drawing in damp air through a filter and over a cooling element which changes it into water droplets.It can produce up to 12 liters a day.The Water Mill will also produce more water when storms pass over, as the humidity in the air increases.In keeping with its ecodevelopment,the machine uses the same amount of electricity as three light bulbs. Inventor Jonathan Ritchey said:"The demand for water is .People are looking for freedom from water distribution systems that are shaky and unreliable". The machine,which is about 3 feet wide,is likely to costPS800 when it goes on sale here in the spring.Its maker, Canadian firm Element Four, estimates that a liter of water will cost around 20 pence to produce. Environmentalists claim half the world's population will face water shortage because of climate change by 2080.One in five humans is said to lack access to safe drinking water. The Water Mill is not effective in areas with below about 30 percent relative humidity, but with average relative humidity in England of more than 70 percent that won't be much of an issue here.
Answer: unlimited source
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According to the author, the biggest advantage of the machine is its _ .

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Article: There was a time in my life when beauty meant something special to me. I guess that would have been when I was about six or seven years old, just several weeks or maybe a month before the orphanage turned me into an old man. I would get up every morning at the orphanage, make my bed just like the little soldier that I had become and then I would get into one of the two straight lines and march to breakfast with the other twenty or thirty boys who also lived in my dormitory. After breakfast one Saturday morning I returned to the dormitory and saw the house parent chasing the beautiful monarch butterflies who lived by the hundreds in the bushes scattered around the orphanage. I carefully watched as he caught these beautiful creatures, one after another, and then took them from the net and then stuck straight pins through their head and wings, pinning them onto a heavy cardboard sheet. How cruel it was to kill something of such beauty. I had walked many times out into the bushes, all by myself, just so the butterflies could land on my head, face and hands so I could look at them up close. When the telephone rang the house parent laid the large cardboard paper down on the back cement step and went inside to answer the phone. I walked up to the cardboard and looked at the one butterfly who he had just pinned to the large paper. It was still moving about so I reached down and touched it on the wing causing one of the pins to fall out. It started flying around and around trying to get away but it was still pinned by the one wing with the other straight pin. Finally its wing broke off and the butterfly fell to the ground and just trembled. I picked up the torn wing and the butterfly and I spat on its wing and tried to get it to stick back on so it could fly away and be free before the house parent came back. But it would not stay on him.
Answer: he had sympathy for the beautiful butterfly
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The author set the living butterfly free because _ .

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Article: It is sometimes reported that strange flying objects have been seen high up in the sky. People call these strange objects Unidentified Flying Objects(UFOs). These UFOs caused a lot of interest. Some of the reports about them are difficult to believe.Some have been explained in scientific ways. Others have never been explained. Here is an account of UFOs from a report. Dennis Bardens,who wrote an article,tells us that he once saw a UFO himself.He was having dinner one night with a friend near Tripoli ,Libya ,and after dinner the two men walked across a yard to his room to look at some papers.Bardens noticed that the moon looked strange that night. "It wasn't the moon,"was the reply. They watched the light and saw that it was moving.It seemed to be an object rather like a big plate.In some ways it looked like smoke with a light on it,but it wasn't smoke because it didn't change its shape.It was moving in a regular way.That is to say,it didn't go suddenly faster or more slowly,and it didn't go higher or lower.So the two men decided that there must be men in it. When it came nearer to Libya,Bardens said that he felt eyes looking at him.He was being watched in the darkness. When it was nearer,they noticed that the bottom parts were brighter than the top.The bottom was yellow and the top was red.Then the object suddenly turned away and left Libya,moving very fast. On a later day Bardens talked to other people about it,and he found some who had seen it.They all described it in the same way.Could they all the mistaken?
Answer: strange flying objects
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The UFOs are _ .