Read the article and select the best answer. Article: What will power your house in the future?Nuclear,wind,or solar power?According to scientists at the Massachusetts Institute of Technology (MIT) in the US,it might be leaves -- but artificial ones. Natural leaves are able to change sunlight and water into energy. It is known as photosynthesis .Now researchers have found a way to imitate this seemingly simple process. The artificial leaf developed by Daniel Nocera and his colleagues at MIT can be seen as a special silicon chip with catalysts .Similar to natural leaves,it can split water into hydrogen and oxygen when put into a bucket of water. The hydrogen and oxygen gases are then stored in a fuel cell,which uses those two materials to produce electricity,located either on top of a house or beside the house. Though the leaf is only about the shape of a poker card,scientists claimed that it is promising to be an inexpensive source of electricity in developing countries. "One can imagine villages in India and Africa not long from now purchasing an affordable basic power system based on this technology," said Nocera at a conference of the American Chemical Society. The artificial leaf is not a new idea. The first artificial leaf was invented in 1997 but was too expensive and unstable for practical use. The new leaf,by contrast,is made of cheap materials,easy to use and highly stable. In laboratory studies,Nocera showed that an artificial leaf prototype could operate continuously for at least 45 hours without a drop in activity. The wonderful improvements come from Nocera's recent discovery of several powerful,new and inexpensive catalysts. These catalysts make the energy transformation inside the leaf more efficient with water and sunlight. Right now,the new leaf is about 10 times more efficient at carrying out photosynthesis than a natural one. Besides,the device can run in whatever water is available;that is,it doesn't need pure water. This is important for some countries that don't have access to pure water. With the goal to "make each home its own power... Question: The main idea of this passage is _ . Options: A: an introduction to the history of artificial leaves B: a mixture of water power and solar energy C: giving energy to the poor D: an invention copying photosynthesis
D

Read the article and select the best answer. Article: HOUSTON (Reuters) -- Houston tops a U.S. magazine's annual fattest cities list for the fourth time in five years, with four other Texas cities in the top 25. Fast food restaurants -- Houston has twice the national average number -- are partly to blame for the dishonor,Men's Fitnesseditor-in-chief Neal Boulton said. "Americans work long hours, don't take vacations, and when they're faced with the worst food choices, they indulge in those," he said. High humidity, poor air quality and some of the nation's longest commute times also helped Texas' most populous city unseat Detroit, the 2003 heavy weight champion, the magazine said. Houston Mayor Bill White, who has worked with a major food company to develop healthy food products and the city's public schools to improve lunch menus, called the report "mostly ungrounded and nonsense." "On the other hand, it calls attention to real issues the mayor is trying to deal with," his spokesman, Frank Michel, said. The magazine said it looked at factors such as the number and types of restaurants, park space, air quality, weather and the number of health clubs. Philadelphia, Detroit, Memphis, Tennessee, and Chicago followed Houston on the seventh edition of the fat list. Texas cities Dallas, San Antonio, Fort Worth and El Paso were in the top 14, which Boulton said was no surprise. "It's pure big indulgence, just _ , and that's part of the culture," said Boulton. Seattle ranked as the fittest city. Austin and Arlington, a Dallas-Fort Worth suburb, were the only Texas cities on the fit list. Austin was 19th and Arlington 22nd out of 25. Question: Which of the following is best supported by the text? Options: A: Texas has the most fat cities in the U.S. B: Bill White is happy with the newspaper report. C: People in Texas are the most hardworking in the U.S. D: Most school children in Houston have weight problems.
A

Read the article and select the best answer. Article: Experts recently suggested that teens should start adopting early bedtimes. Before you dismiss it as a habit suited only for young kids, consider that there are serious advantages in being well-rested. And now, even more research suggests that putting phones away before going to sleep is important to teens' well-being. A new study from Seton Hall University School of Health and Medicine Science found that 62 percent of kids used their smart phones before bed, and it's causing less sleep and poor performance in school. Those teens who text before bedtime tend to go to sleep later, and get up later in the morning. Such behavior can be associated with mental health issues like depression or anxiety. Besides, once teens do receive a text, experts found, they tend to respond right away. Then the text conversation continues -- resulting in an even later bedtime. The study's co-author Dr. Peter Polos says this leads to excessive stimulation at night. Light from electronic devices can block the secretion of melatonin -- a hormone that promotes sleep, which makes sleep difficult in the face of overuse of smart phones at night. It's true! More screen time means less sleep time; other studies have suggested the same idea. As for a final piece of advice, Dr. Sushanth Bhat says, since getting the proper amount of sleep is very important for brain development and learning in the teenage years, our study should encourage parents and guardians to limit adolescent smart phone usage at night. Keep in mind that teens aren't the only ones addicted to their phones! Adults can also benefit from setting a tech curfew for themselves. After all, kids learn by example! Question: Melatonin can _ . Options: A: make sleep difficult B: lead to later bedtimes C: help people fall asleep D: wake people from a sleep
C