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.

Input: Consider Input: 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

Output: According to the author, the biggest advantage of the machine is its _ .

Input: Consider Input: Article: The place is England. The year is 1928. One of the founding theorists of quantum mechanics , Paul Dirac, is scratching his head because solutions to his equations have _ unexpected results. For the solutions to make sense, he reasons, there must be a particle that has the mass of an electron but the opposite charge. At the time, such a thing was not known to exist. Several years pass before American physicist Carl Anderson observes a "positive" electron, or positron that confirms Dirac's prediction. Antimatter , as the name implies, can be described as the opposite of ordinary matter. Every particle in the universe has characteristics such as mass and charge. With antimatter, the mass remains constant, but the sign of the charge is reversed. All particles have an antimatter counterpart , even the chargeless neutron . Unlike matter, antimatter is not common. Unless you're in the upper atmosphere, or inside a particle accelerator, you're not going to come across it. "Antimatter was not always so rare," Stephane Coutu, Penn State particle physicist says. There was a time when it was as prevalent as matter itself. "Right after the Big Bang ," Coutu explains, "we believe there must have been exactly the same amounts of matter and antimatter...and yet owing to some small asymmetry in the laws of particle interactions, all of the antimatter and most of the matter in the early universe was annihilated . We are left today with the resulting matter-dominated universe." Science fiction is rife with tales of high-energy particle annihilation, and indeed, antimatter weapons have appeared in current bestselling novels. This is unrealistic, Coutu says. "[It] would be very impractical owing to very great difficulties in producing and maintaining significant amounts of antimatter." Technology that uses the properties of antimatter is actually feasible outside of science fiction, however. Positron emission tomography (PET) is a medical technique that can be used to detect cancer, measure blood flow and detect coronary artery disease. While antimatter may never be used as a bomb, it certainly has a positive future in life-saving medical diagnostic tools, the anti-weapon.
Answer: It's not easy to produce and maintain large quantities of antimatter

Output: According to Coutu, _ .

Input: Consider Input: Article: You know that balloons must be kept away from sharp objects. They also needed to be kept away from flames. A fire can weaken the rubber and cause it to break. However, in this experiment you will find out how you can hold a balloon directly in a flame without breaking the balloon. Materials needed: * two round balloons not inflated * several matches * water Inflate one of the balloons and tie it. Place 1/4 cup of water in the other balloon, and then inflate it and tie it. Light a match and hold it under the first balloon. Allow the flame to touch the balloon. What happens? The balloon breaks, perhaps even before the flame touches it. Light another match. Hold it directly under the water in the second balloon. Allow the flame to touch the balloon. What happens to this balloon? It doesn't break. Why does the balloon with no water break in the flame? The flame heats the rubber of both balloons. The rubber of the balloon without water becomes so hot that it becomes too weak to _ the pressure of the air inside the balloon. However, when the balloon with water in it is placed in the flame, the water takes in most of the heat from the flame. Then, the rubber of the balloon doesn't become very hot, it doesn't weaken, and the balloon doesn't break. Water is a particularly good absorber of heat. It takes a lot of heat to change the temperature of water. On the other hand, when water cools, it gives off a great deal of heat. That's why areas near oceans or other large bodies of water don't get as cold in winter as areas at the same latitude further inland.
Answer: time
Output: From the passage we can know the following aspects of the experiment except _ .