Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Example Input: Context: The major cause of outdoor air pollution is the burning of fossil fuels. Fossil fuels are burned in power plants, factories, motor vehicles, and home heating systems. Ranching and using chemicals such as fertilizers also cause outdoor air pollution. Erosion of soil in farm fields, mining activities, and construction sites adds dust particles to the air as well. Some specific outdoor air pollutants are described in Table 25.1. Air Pollutant Sulfur oxides Nitrogen oxides Carbon monoxide Carbon dioxide Particles (dust, smoke) Mercury Smog Ground-level ozone Source coal burning motor vehicle exhaust motor vehicle exhaust all fossil fuel burning wood and coal burning coal burning coal burning motor vehicle exhaust Problem acid rain acid rain poisoning global climate change respiratory problems nerve poisoning respiratory problems respiratory problems Outdoor air pollution causes serious human health problems. For example, pollutants in the air are major contributors to respiratory and cardiovascular diseases. Air pollution may trigger asthma attacks and heart attacks in people with underlying health problems. In fact, more people die each year from air pollution than automobile accidents. Air pollution may also cause acid rain. This is rain that is more acidic (has a lower pH) than normal rain. Acids form in the atmosphere when nitrogen and sulfur oxides mix with water in air. Nitrogen and sulfur oxides come mainly from motor vehicle exhaust and coal burning. If acid rain falls into lakes, it lowers the pH of the water and may kill aquatic organisms. If it falls on the ground, it may damage soil and soil organisms. If it falls on plants, it may make them sick or even kill them. Acid rain also damages stone buildings, bridges, and statues, like the one in Figure 25.1. Another major problem caused by air pollution is global climate change. Gases such as carbon dioxide from the burning of fossil fuels increase the greenhouse effect and raise Earths temperature. The greenhouse effect is a natural feature of Earths atmosphere. It occurs when certain gases in the atmosphere, including carbon dioxide, radiate the suns heat back down to Earths surface. Figure 25.2 shows how this happens. Without greenhouse gases in the atmosphere, the heat would escape into space. The natural greenhouse effect of Earths atmosphere keeps the planets temperature within a range that can support life. The rise in greenhouse gases due to human actions is too much of a good thing. It increases the greenhouse effect and causes Earths average temperature to rise. Rising global temperatures, in turn, are melting polar ice caps and glaciers. Figure 25.3 shows how much smaller the Arctic ice cap was in 2012 than it was in 1984. With more liquid water on Earths surface, sea levels are rising. Adding more heat energy to Earths atmosphere also causes more extreme weather and changes in precipitation patterns. Global warming is already causing food and water shortages and species extinctions. These problems will only grow worse unless steps are taken to curb greenhouse gases and global climate change. You may be able to avoid some of the health effects of outdoor air pollution by staying indoors on high-pollution days. However, some indoor air is just as polluted as outdoor air. One source of indoor air pollution is radon gas. Radon is a radioactive gas that may seep into buildings from rocks underground. Exposure to radon gas may cause lung cancer. Another potential poison in indoor air is carbon monoxide. It may be released by faulty or poorly vented furnaces or other fuel-burning appliances. Indoor furniture, carpets, and paints may release toxic compounds into the air as well. Other possible sources of indoor air pollution include dust, mold, and pet dander. Its easier to control the quality of indoor air than outdoor air. Steps home owners can take to improve indoor air quality include: keeping the home clean so it is as free as possible from dust, mold, and pet dander. choosing indoor furniture, flooring, and paints that are low in toxic compounds such as VOCs (volatile organic compounds). making sure that fuel-burning appliances are working correctly and venting properly. installing carbon monoxide alarms like the one in Figure 25.4 at every level of the home. 
 Question: __toxic gas that may be released by faulty fuel-burning appliances
Example Output: carbon monoxide

Example Input: Context: Sir Balan le Savage, brother of Sir Balin from Northumberland, is a minor character mentioned in various Arthurian legends. 
 Question: Who was the brother of Sir Balan?
Example Output: sir balin

Example Input: Context: Set in the Australian outback in the 1880s, the movie follows the series of events following the horrific rape and murder of the Hopkins family, allegedly committed by the infamous Burns brothers gang.The film opens in a brothel during a violent gunfight between the police and Charlie Burns' (Guy Pearce) gang, which ends with the deaths of all of the gang members except for Charlie and his younger brother Mikey. Captain Stanley (Ray Winstone) proposes to Charlie: he and Mikey can go free of the crimes they have committed if Charlie kills his older brother, Arthur (Danny Huston). Arthur is a mercurial psychopath who has become something of a legend and is so vicious that the Aboriginal tribes refer to him as "The Dog Man" and both the police and the Aboriginals refuse to go near his camp. Captain Stanley muses that perhaps the bounty hunters will kill Arthur in time and then states his intention to civilize the harsh Australian wilderness by bringing Arthur to justice and using Mikey as leverage. Charlie has nine days to find and kill Arthur, or else Mikey will be hanged from the gallows on Christmas Day.We discover why Captain Stanley is intent on taming Australia: he has been forced to move there with his delicate wife, Martha Stanley (Emily Watson), and apparently wants to make it an appropriate place for them to live. The Stanleys were also friends of the Hopkins family, leading Martha to have nightmares about her dead friends and the unborn child one of them is revealed to have carried. Word spreads of Stanley's deal with Charlie, primarily from Stanley's corrupt subordinate, Sergeant Lawrence (Robert Morgan), causing disgust among the townspeople.Shortly thereafter, Eden Fletcher (David Wenham), for whom Captain Stanley works, orders that Mikey be given one hundred lashes as punishment for the rape and murder of the Hopkins family. Stanley is aghast at this, not only because he believes that Mikey is innocent and the flogging will surely kill him, but because it would also break his deal with Charlie and thus put him and his wife in grave danger. Stanley sends Sergeant Lawrence away with tracker Jacko (David Gulpillil) and other men to "investigate" the reported slaying of Dan O'Riley by a group of Aborigines. Captain Stanley attempts to defend Mikey by gunpoint from the bloodthirsty townspeople, but is overruled once Martha arrives, insisting on revenge for her dead friends. Mikey is then brutally flogged, and horrifically wounded. The formerly excited townspeople slowly become disgusted and Martha faints at the ghastly display. After 40 lashes, Mikey has collapsed and the whip is soaked with blood. Captain Stanley grabs the whip and throws it at Fletcher, staining his face and suit with blood, who in turn fires Stanley.Meanwhile, Charlie rides a great distance in search of Arthur, drinking and apparently reflecting on what he will do. Along the way, he encounters an inebriated old man named Jellon Lamb (John Hurt). In the course of conversation, Charlie realizes that Lamb is a bounty hunter in pursuit of the Burns brothers and knocks him out. Later on, after sleeping on a rock bed, Charlie awakes and, before he can gather what's going on, is speared in the chest by a group of Aboriginal men standing over him. Seconds later a gunshot is heard and the head of the man who threw the spear explodes. Charlie then passes out.Charlie wakes up in the camp of his brother Arthur, which is located in caves among desolate mountains. Arthur's gang consists of Samuel Stoat (Tom Budge), who shot the Aboriginal man who had speared Charlie; a woman named Queenie (Leah Purcell) who tends to Charlie's wound; and a muscular Aboriginal man called Two-Bob (Tom E. Lewis). As he recovers from his wounds, Charlie has several opportunities to kill his brother, but does not. Not too far away from Arthur's camp, Sergeant Lawrence and his men have found and butchered a group of Aborigines. Arthur and Two-Bob find Lawrence's group while they sleep, ostensibly to get a horse for Charlie, and proceed to kill Jacko and Sergeant Lawrence. Before Arthur stomps Lawrence 
 Question: Who is a bounty hunter?
Example Output:
lamb