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: Asia has many wild places. The following national parks are among the most famous in Asia. People come to visit them from near and far in order to appreciate the unique qualities of the land and everything on it. Have you ever visited any of these Asian national parks? Jiuzhai Valley National Park, China The extraordinarily beautiful park is famous for its fascinating blue-green lakes, waterfalls and its unique wildlife. Located in the Minshan Mountain, Sichuan Province, it is a breathtaking park because of its scenery and it is also home to nine Tibetan villages, over 220 bird species as well as a number of endangered animals and plants, such as giant pandas, Sichuan golden monkeys and numerous _ . This park was also declared a UNESCO World Heritage Site in 1992. Khao Sok National Park, Thailand This extraordinary park is several miles away from Phuket , yet its remoteness prevents it from being visited. Even so, it is well worth a visit as scientists have noted that is rainforest stretches are not only longer than those of the Amazon, but also more divers . Animals like tigers, Asian elephants, and macaaues make their home here. Everyone who visits the park, however, seems to want to have a look at the amazing Rafflesia, one of the strangest flowering plants on earth; it smells like smelly meat when it blooms. Nikko National Park, Japan It is lovely to visit this park all the year round with its waterfalls and picturesque Lake Chuzenji. And it is especially worth visiting in autumn when the leaves change from green to deep red and orange. Set with UNESCO protected shrines and temples, the park is a unique mixture of natural and man-made attractions. With various routes perfect for adventurous hikers, a visit to the Nikko National Park is not to be missed. If you want to know more information about Asian famous national parks, you can log in [Link] If you want to enjoy all the above, welcome to call 050-24689120, and we can give a reasonable price. 
 Question: If you're an adventurous hiker, which park would you probably choose to visit?
Example Output: nikko national park.

Example Input: Context: The objective of this study was to analyze the expression levels of multiple components in the mammalian target of rapamycin (mTOR) signaling pathway in radical nephrectomy specimens from patients with metastatic renal-cell carcinoma (RCC) treated with mTOR inhibitors in order to identify factors predicting susceptibility to these agents. This study retrospectively included a total of 48 consecutive patients undergoing radical nephrectomy, who were diagnosed with metastatic RCC and subsequently treated with an mTOR inhibitor (everolimus or temsirolimus) as either first- or second-line systemic therapy. Expression levels of 5 molecular markers involved in the signaling pathway associated with mTOR, including PTEN, phosphorylated (p)-Akt, p-mTOR, p-p70 ribosomal S6 kinase, and p-4E-binding protein 1 (4E-BP1), were measured by immunohistochemical staining of primary RCC specimens. Of several factors examined, bone metastasis, liver metastasis, and the expression level of p-4E-BP1 were shown to have significant impacts on the response to the mTOR inhibitors. Progression-free survival (PFS) was significantly correlated with the expression levels of PTEN and p-4E-BP1 in addition to the presence of bone metastasis on univariate analysis. Of these significant factors, p-4E-BP1 expression and bone metastasis appeared to be independently associated with PFS on multivariate analysis. These findings suggest that it would be useful to consider the expression levels of potential molecular markers in the mTOR signaling pathway, particularly p-4E-BP1, as well as conventional clinical parameters when selecting patients with metastatic RCC who are likely to benefit from treatment with mTOR inhibitors. 
 Question: What does mTOR stands for?
Example Output:
mammalian target of rapamycin