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 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
According to Coutu, _ .

Article: CARDIFF, Wales Poets, singers and musicians from across the globe gathered in Wales to celebrate the tradition of storytelling. "It might seem strange that people still want to listen in age of watching television, but this is an unusual art form whose time has come again," said David Ambrose, director of Beyond the Border, an international storytelling festival in Wales. "Some of the tales, like those the Inuit from Canada, are thousands years old. So our storytellers have come from distant lands to connect us with the distance of time," he said early this month. Two Inuit women, both in their mid 60s, are among the few remaining who can do Kntadjait, or throat singing, which has few words and much sound. Their art is governed by the cold of their surroundings, forcing them to say little but listen attentively. Ambrose started the festival in 1993, after several years of working with those reviving (coming back into use or existence) storytelling in Wales. "It came out of a group of people who wanted to reconnect with traditions. and as all the Welsh are storytellers, it was _ here." Ambrose said.
Answer: will be popular again
Ambrose believes that the art of storytelling _ .

Article: It is a reply to a letter written by Zhai Mingjun, a 16-year-old girl in the class. The two astronauts thank the student for her concerns and wish the class luck in their future studies. "I' m so happy that the two space men replied with a few encouraging words," said Zhai. Her letter was one of the 10 winning letters taken into space by Fei and Nie, who have succeeded in traveling space in the Sixth Shenzhou Spaceship. Zhai wrote the letter as if she were a younger sister of the astronauts. "As the single child in my family, I always hoped that I would have an elder brother that I could be proud of," Zhai said. "I thought that the astronauts would be lonely during such a long space trip. I hoped they would feel happy and warm when reading my letter." Many of Zhai' s classmates also wrote their words of encouragement and admiration to the astronauts. "The letter to the astronauts made us believe that we can also be part of the manned space programme," said Zhao Dongxu. All the students have high expectations for China' s future space programme. "I heard that Snoopy is the mascot for US astronauts. I hope I can design a mascot for our heroes," said Liu Mengjie, 16. "A physics class taught by astronauts in outer space would be very interesting. I want to be the astronaut who teaches students about zero gravity with my head upside down in the spaceship," said Han Yinan. Many students think that the manned space program is still far away from them. But they feel proud that ordinary students could participate in such a great scientific achievement and hope there will be more possibilities to take part.
Answer: A reply from space
The best title of this passage can be _ .