Some trees can survive a long time without water. Think of trees that grow in the desert. But other trees may need more moisture  than they can get from rainfall or from the air . Trees and other plants can look thirsty. Leaves can become weak and hang downward. They can also turn yellow. Yellowing can be a sign of too much water. But it can also be a warning sign of too little water. With a newly planted tree, the roots have not yet spread out from the root ball. The root ball can become dry faster than the dirt around it. So put water on the area of the root ball and the surrounding soil until the roots become established. Once a tree is well established, water deeply instead of watering often. The amount of water needed depends on the tree and the soil. Clay  soils hold water for longer periods while sandy soil holds less water. During the hottest season, a deep watering may satisfy a tree for anywhere from ten days to four weeks. Ted Swiecki is a plant scientist . He says people should not water established trees at the base of the trunk . This can harm the tree. Too much water in the soil at the base of a tree can lead to the growth of fungi . If the area is too wet, harmful organisms have a better chance to invade the tree and cause disease. Mr. Swiecki says this is true especially in Mediterranean and semi-dry climates. Many trees in these climates have adapted to having a dry area near their base during the hottest season. He said, "Water displaces (,)air in the soil. And roots are aerobic ; they require oxygen for the soil to function properly. So if you keep the soil completely wet and there's no air there, then the roots are starving for oxygen." As to a well-established tree,   _  . A) watering deeply matters more than watering often B) we should water them as often as possible C) its roots have not spread out from the root ball yet D) a deep watering satisfies it for at most ten days in cold weather
A


At least 10 million hectares of cultivated land in China are polluted, which makes a _ threat to the country's food safety, the Xinhua News Agency reported on Friday. The polluted land,which is mostly in economically developed areas,accounts for one-tenth of the country's total arable land,according to an incomplete survey by the State Environmental Protection Administration,China's top environment watchdog. Pollution on cultivated land threatens the environment,food safety and the sustainable development of agriculture,the administration said. Because of continual,too much use of chemical fertilizer, pesticide and agricultural plastic sheeting, as well as irrigation using polluted water, a large amount of contaminants remain in the cultivated land. The contaminants affect the soil's ecological structure and function,leading to decreased soil productivity, lower crop yield ,and lower quality of agricultural products- It also leads to worse water quality in rural areas. Less than 9 per cent of drinkable water passed checks for bacteria in243 rural water supply stations across the county. Another survey, which took samples of drinking water and groundwater an 69 small towns.  in Beijing, Tianjin and Hebei Province of North,China, showed that more than half of the water contains too much nitrate ,which may cause diabetes and damage the kidney. The administration estimated at least 1 90 million farmers are drinking water that contains harmful substances. Many villagers drink unfiltered water taken from shallow water wells or water cellars, which are reported to have poor sanitary conditions* The author writes the passage to  _  . A) 1et the readers examine their mistakes B) present the readers a new idea C) come up with a solution to ending farmland pollution D) inform the readers of the importance of fighting farmland pollution
D


Q: It's hard to track the blue whale, which has almost been killed off by commercial whaling. Attaching radio devices to it is difficult and visual sightings are too unreliable to give real insight into its behavior. So biologists were delighted early this year when, with the help of the US Navy, they are able to track a particular blue whale for 43 days recording its sounds. This was possible because of the Navy's former top secret system of underwater listening devices across the oceans. Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies. Earth scientists announced at a news conference recently that they had used the system for closely observing a deep-sea volcanic eruption for the first time and that they planned similar studies. Other scientists have proposed to use the network for tracking ocean currents and measuring changes in the ocean and global temperatures. Different layers of ocean water can act as channels for sounds focusing them in the same way a stethoscope  does when it carries faint noises from a patient's chest to a doctor's ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles. What can we infer from the passage? A) New radio devices are developed for tracking the blue whales. B) Blue whales are no longer endangered with the new system. C) Opinions differ on the use of military technology. D) Military technology has great potential in civilian use.
A: D


Question: Don't you think it interesting that there were strange coincidences  in the deaths of President Kennedy and President Lincoln? For example, John Kennedy was elected president in 1960 while Abraham Lincoln in 1860, between which was a hundred years. Both men were killed from behind, on black Friday , and with their wives on the spot. The two men were born exactly one hundred years away, as were their murderers, Lee Oawald and John Booth. Perhaps the strangest coincidence is that President Kennedy's secretary , whose name was Lincoln, advised the president not to go to Dallas, where the president was shot. President Lincoln's secretary, named Kennedy, advised the president not to go to the Ford Theatre, where the president met his death. "Black Friday" means that   _  . A) the American used to be in black on the two Fridays. B) the two Fridays saw sad happenings C) it was dark when the two men were killed D) it was cloudy when the two men were killed
Answer: B


*Question*
We all know how important human life is--it's priceless. Firstly, we can tell you that the lives of your relatives could depend on your ability to give first aid. If you think highly of human's life, this article is for you! Here you can find information about first aid. The very first thing that you should do when you see an accident is to _ the situation and prevent further dangerous incidents. First of all, you have to recognize what has happened and what the dangers to rescuers and victims are. Think about how to take care of the victims. Helping usually takes place in very difficult conditions and injuries can be very bad. Therefore, you cannot be too afraid of making mistakes to help. Sometimes you have to face the fact that regardless of   your actions and your efforts the victim's condition might not improve--he or she could even die. In some cases even professional medical aid may not succeed. If you have done everything you think you should do, you shouldn't feel guilty. Do not expose yourself to danger. Giving first aid can be dangerous. While trying to help a victim, do not forget about your own safety. If something happens to you, you won't be able to help anyone. Call for help after you find out the condition of a victim. But remember if a victim faints   due to breathing failure caused by drowning, choking or poisoning, you should first take action that helps to bring back the heartbeat and breathing. While calling, talk shortly but clearly. Always provide the following information--the location of the accident, the kind of accident, the number of the injured and your full name and phone number and so on. The author thinks that helping a victim can be  _  . A) exciting B) shocking C) dangerous D) boring
**Answer**

C