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: In the 19thcentury, Americans from the eastern states moved out west to settle in the rich new lands along the Pacific Coast. The most difficult part of their trip was crossing "the Great American Desert" in the western part of the United States by horse and wagon. The western desert can be very dangerous. There is little water and there are few trees. But the desert also has scenery of great beauty. Tall towers of red and yellow stone rise sharply from the flat, sandy valley floor. The scene has been photographed many times and appears in movies and on TV. In Arizona, man-made dams across the Colorado River have made two large lakes in the middle of the dry desert country. At Lake Powell, the red stone arch of Rainbow Bridge rises high above the blue lake. There are few roads. Many areas of Lake Powell's shore can only be reached by boat or on foot. But hikers in this empty desert land sometimes find very old native American pictures, painted on the rocks. In Death Valley, California, the summer temperature rises to 130degF--165degF. There is less than inches of rain each year. Death Valley is the lowest place in America---925 metres below sea level. In the 1800s, many travelers died when they tried to cross this waterless valley in the terrible heat. Although the desert is dry and seems empty, there is plenty of life if you look closely. Snakes and rats have learned how to live in the desert heat. They live underground and come out at night, when it is cool. Plants such as cacti need very little water. When it does rain in the desert (sometimes only once or twice a year), plants grow quickly, and flowers open in a single day. For a short time, the desert is covered with brilliant (very bright) colours.
Answer: wanted to make their home there
In the 19thcentury, Americans moved from east to west because they _ .

Article: We always read reports about costs of oil going up and we will think this is our most valuable material. However, water is the most valuable resource . People in the Middle East are more worried about this than oil. Maybe the next war will be about water. In the future, to control the quality and quantity , you will use different water for different usages. The water used to wash your car, water your flowers or wash your clothes doesn't need to be as clean as the water you drink. One in five people live in countries without enough fresh water and in 25 years, the number is believed to be one in every three people. Our world population is increasing. What do you suppose this will suggest for us in the future? Population control? Traditional management of the water industry has been out of date since the 1990s. When technologies develop so rapidly in the world, we have loads of information for technologies in the business world, but in the water industry we don't have any. Britain and France have already taken measures to successfully improve their water industries. All the water services in Britain have been provided by private companies since 1991. Since then, improvement has been made in the rules for their water quality and pricing. What can you do now for the future? Using water more efficiently in your house can make a great difference not only to the world but to your money. Even if you don't have to pay much now, you will when you start to pay big prices for different water usages.
Answer: the world population is growing up.
Water shortage is getting more serious because _ .

Article: New findings suggest that brainy card games such as contract bridge may temporarily raise production of a key blood cell including in fighting off illness. After 90 minutes of play, bridge players had increased levels of immune cells, according to the research reported last week. A researcher, Diamond, studied bridge players from a women's bridge club. She chose bridge players because the game includes skills stimulating a part of the brain called the dorsolateral cortex. Earlier animal research suggests that this part of the brain may play a role in the immune system. The findings are based on blood samples drawn from 12 women players. Their blood samples showed a rise in levels of white blood cells called T cells after they played bridge for 90 minutes. T cells are produced by the thymus gland and used by the immune system against diseases. The T cell count jumped significantly in eight of the bridge players, and slightly in the other four. The findings contribute to the field of neuroimmunology , whose name reflects the fact that the nervous system and the immune system are not considered separate and isolated systems. What isn't clear is whether the help to the immune system from an activity like contract bridge is lasting or temporary. It is also not clear whether the increase in T cells could finally be targeted against special illnesses.
Answer: raise production of a key blood cell
Playing bridge can help one to fight off diseases because it can _ .