instruction:
In this task, you're expected to write answers to questions involving multiple references to the same entity. The answer to the question should be unambiguous and a phrase in the paragraph. Most questions can have only one correct answer.
question:
Passage: After the Southwest became part of the U.S., explorers continued to look for good east–west routes along the 35th parallel. In 1853, a crew led by U.S. Army Lieutenant Amiel Whipple surveyed along a sandy wash in the northern part of the Petrified Forest. So impressed was Whipple by the petrified wood along the banks of the arroyo that he named it Lithodendron Creek (Stone Tree Creek). Geologist Jules Marcou, a member of the Whipple expedition, observed that the petrified trees were from the Triassic.A slightly later route along the parallel was a wagon road, built between 1857 and 1860, that involved experimental use of camels as transport. In the late 19th century, settlers and private stagecoach companies followed similar east–west routes. Homesteaders who stayed in the area developed cattle ranches on the grasslands, and cattle grazed in the Petrified Forest until the mid-20th century.Also close to the 35th parallel was the Atlantic and Pacific Railroad. Its opening in the early 1880s led to the founding of towns like Holbrook and Adamana. Visitors could stop at the Adamana train station, book a hotel room, and take a tour of what was then called the Chalcedony Forest. Over the years, the line changed hands, becoming the Atchison, Topeka and Santa Fe Railway, and then the BNSF. More than 60 BNSF trains, mostly carrying freight, pass through the park every day. U.S. Route 66, a former transcontinental auto highway developed in 1926 from part of the National Old Trails Road, ran parallel to the railroad tracks until it was decommissioned in 1985. The park has preserved within its boundaries a small grassy section of the road. Interstate 40, which crosses the park, replaced the older highway. 
Question: What is the name of the place that 60 BNSF trains pass through everyday?
answer:
Petrified Forest.


question:
Passage: Most historians describe the contacts between the Mongol Empire and the Western Europeans as a series of attempts, missed opportunities, and failed negotiations. Christopher Atwood, in the 2004 Encyclopedia of Mongolia and the Mongol Empire, summed up the relations between Western Europe and the Mongols: "Despite numerous envoys and the obvious logic of an alliance against mutual enemies, the papacy and the Crusaders never achieved the often-proposed alliance against Islam."A few other historians argue there was an actual alliance, but do not agree on the details: Jean Richard wrote that an alliance began around 1263. Reuven Amitai stated that the closest thing to actual Mongol-Frankish military coordination was when Prince Edward of England attempted to coordinate activities with Abaga in 1271. Amitai also mentioned the other attempts towards cooperation, but said, "In none of these episodes, however, can we speak of Mongols and troops from the Frankish West being on the Syrian mainland at the same time." Timothy May described the alliance as having its peak at the Council of Lyon in 1274, but that it began to unravel in 1275 with the death of Bohemond, and May too admitted that the forces never engaged in joint operations. Alain Demurger, in his own book The Last Templar, said that an alliance was not sealed until 1300.There also continues to be debate about whether or not an alliance would have been a wise idea, and whether the Crusaders at that point in history were even relevant to the Persian-Mongol conflict. The 20th-century historian Glenn Burger said, "The refusal of the Latin Christian states in the area to follow Hethum's example and adapt to changing conditions by allying themselves with the new Mongol empire must stand as one of the saddest of the many failures of Outremer." This was similar to the view of Steven Runciman, who argued, "Had the Mongol alliance been achieved and honestly implemented by the West, the existence of Outremer would almost certainly have been prolonged. The Mameluks would have been crippled if not destroyed; and the Ilkhanate of Persia would have survived as a power friendly to the Christians and the West". However, David Nicolle, describing the Mongols as "potential allies", said that early historians were writing from the benefit of hindsight, and that overall the major players were the Mamluks and the Mongols, with Christians just "pawns in a greater game.". 
Question: Who did Jean Richard claim had an alliance around 1263?
answer:
Mongol Empire.


question:
Passage: The impact would have caused a megatsunami over 100 metres (330 ft) tall that would have reached all the way to what are now Texas and Florida. The height of the tsunami was limited by the relatively shallow sea in the area of the impact; in deep ocean it would have been 4.6 kilometres (2.9 mi) tall. A cloud of super-heated dust, ash and steam would have spread from the crater as the impactor burrowed underground in less than a second. Excavated material along with pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon re-entry, broiling the Earth's surface and possibly igniting wildfires; meanwhile, colossal shock waves would have triggered global earthquakes and volcanic eruptions. Fossil evidence for an instantaneous die-off of diverse animals was found in a soil layer only 10 centimetres (3.9 in) thick in New Jersey some 5,000 kilometres (3,100 mi) away from the impact site, indicating that death and burial under debris occurred suddenly and quickly over wide distances on land.The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. The shock production of carbon dioxide caused by the destruction of carbonate rocks would have led to a sudden greenhouse effect. Over a decade or longer, sunlight would have been blocked from reaching the surface of the Earth by the dust particles in the atmosphere, cooling the surface dramatically. Photosynthesis by plants would also have been interrupted, affecting the entire food chain. A model of the event developed by Lomax et al. (2001) suggests that net primary productivity (NPP) rates may have increased to higher than pre-impact levels over the long term because of the high carbon dioxide concentrations.In February 2008, a team of researchers led by Sean Gulick at the University of Texas at Austin's Jackson School of Geosciences used seismic images of the crater to determine that the impactor landed in deeper water than was previously assumed. They argued that this would have resulted in increased sulfate aerosols in the atmosphere. According to the press release, that "could have made the impact deadlier in two ways: by altering climate (sulfate aerosols in the upper atmosphere can have a cooling effect) and by generating acid rain (water vapor can help to flush the lower atmosphere of sulfate aerosols, causing acid rain)." This was borne out by the results of a drilling project in 2016 which found that sulfate-containing rocks found in the area were not found in the peak ring (the rocks found were from deep within the earth's crust instead), the interpretation being that they had been vaporized by the impact and dispersed into the atmosphere. 
Question: What in the atmosphere would have blocked sunlight from reaching the surface of the Earth?
answer:

dust particles.