Input: The inhabited history of the Las Vegas Valley stretches to 23,000 b.c. , when much of the area was covered by a prehistoric lake. During this period, the indigenous people lived in caves, hunting the mammals that gathered at the shoreline. The landscape of the valley changed dramatically over the next 200 centuries. The glaciers feeding the lake melted away and the lake evaporated. Fossils tell an obscure story of man's slow and sporadic development. Around 3000 b.c. , native Archaic Indians began to develop a lasting hunting and gathering culture. By this time, the valley was in much the same geographic state as it exists in today, with one exception — the presence of artesian springs that bubbled to the surface in several areas. These springs fed a network of streams draining through the Las Vegas Wash to the Colorado River. The areas surrounding the springs were desert oases: sprawling collections of grasses, trees, and wildlife. Many springs lay in areas that would eventually become the center of the modern Las Vegas metropolis. For about 4000 years, the Archaics thrived in a culture that included many signs of early civilization. Signs of even more advancement appeared halfway through the first millennium a.d. , when the Anasazi Indians inhabited the valley. Far more progressive than the Archaics, the Anasazi utilized such formal agricultural techniques as irrigation to assist their harvest. This permitted the Anasazi to achieve a benchmark of advanced society — the ability to live in permanent shelters year-round without need to follow wildlife. Mysteriously, the Anasazi vanished from the valley around a.d. 

Does the response "23,000 b.c" correctly answer the question "Approximately what year was the Las Vegas Valley covered by a prehistoric lake?"?

OPTIONS:
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Output: yes
Not until 1998 did al Qaeda undertake a major terrorist operation of its own, in large part because  Bin Laden lost his base in Sudan. Ever since the Islamist regime came to power in Khartoum, the United States and other Western governments had pressed it to stop providing a haven for terrorist organizations. Other governments in the region, such as those of Egypt, Syria, Jordan, and even Libya, which were targets of some of these groups, added their own pressure. At the same time, the Sudanese regime began to change. Though Turabi had been its inspirational leader, General Omar al Bashir, president since 1989, had never been entirely under his thumb. Thus as outside pressures mounted, Bashir's supporters began to displace those of Turabi. The attempted assassination in Ethiopia of Egyptian President Hosni Mubarak in June 1995 appears to have been a tipping point. The would-be killers, who came from the Egyptian Islamic Group, had been sheltered in Sudan and helped by  Bin Laden. When the Sudanese refused to hand over three individuals identified as involved in the assassination plot, the UN Security Council passed a resolution criticizing their inaction and eventually sanctioned Khartoum in April 1996. A clear signal to  Bin Laden that his days in Sudan were numbered came when the government advised him that it intended to yield to Libya's demands to stop giving sanctuary to its enemies.  Bin Laden had to tell the Libyans who had been part of his Islamic army that he could no longer protect them and that they had to leave the country. Outraged, several Libyan members of al Qaeda and the Islamic Army Shura renounced all connections with him.  Bin Laden also began to have serious money problems. International pressure on Sudan, together with strains in the world economy, hurt Sudan's currency. Some of  Bin Laden's companies ran short of funds. As Sudanese authorities became less obliging, normal costs of doing business increased. Saudi pressures on the  Bin Laden family also probably took some toll. In any case,  Bin Laden found it necessary both to cut back his spending and to control his outlays more closely. 

Question: "What is the name of the Islamist regime that came to power in Khartoum?"

OPTIONS:
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Answer: "Sudanese"

Response: yes
Heat supplies the energy that causes motion. The deeper you go into toward the Earths core, the hotter it gets. At the core it is really hot. All that heat tries to rise toward the surface. In the Mantle, the rock is partially melted and is able to move. As it is heated, the material in the mantle moves toward the surface. As the mantle material rises, it cools. When it reaches the Earths crust, it is mostly stopped. A little of the material can break through the surface, but not all. Instead, it begins to move horizontally. The mantle material moves horizontally away from a mid-ocean ridge crest. Toward the surface, the mantle material starts to cool. As it cools it sinks back down into the mantle. These areas are where deep sea trench occur. The material sinks back down to the core. The system operates like a giant conveyor belt. The motion due to heating and cooling is called convection. 

Question: "Why does the system work as a conveyor belt?"

Response: "Because the material moves horizontally"
OPTIONS:
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A: no
The hijackers attacked at 9:28. While traveling 35,000 feet above eastern Ohio, United 93 suddenly dropped 700 feet. Eleven seconds into the descent, the FAA's air traffic control center in Cleveland received the first of two radio transmissions from the aircraft. During the first broadcast, the captain or first officer could be heard declaring "Mayday" amid the sounds of a physical struggle in the cockpit. The second radio transmission, 35 seconds later, indicated that the fight was continuing. The captain or first officer could be heard shouting:" Hey get out of here-get out of here-get out of here." On the morning of 9/11, there were only 37 passengers on United 93-33 in addition to the 4 hijackers. This was below the norm for Tuesday mornings during the summer of 2001. But there is no evidence that the hijackers manipulated passenger levels or purchased additional seats to facilitate their operation. The terrorists who hijacked three other commercial flights on 9/11 operated in five-man teams. They initiated their cockpit takeover within 30 minutes of takeoff. On Flight 93, however, the takeover took place 46 minutes after takeoff and there were only four hijackers. The operative likely intended to round out the team for this flight, Mohamed al Kahtani, had been refused entry by a suspicious immigration inspector at Florida's Orlando International Airport in August. Because several passengers on United 93 described three hijackers on the plane, not four, some have wondered whether one of the hijackers had been able to use the cockpit jump seat from the outset of the flight. FAA rules allow use of this seat by documented and approved individuals, usually air carrier or FAA personnel. We have found no evidence indicating that one of the hijackers, or anyone else, sat there on this flight. All the hijackers had assigned seats in first class, and they seem to have used them. We believe it is more likely that Jarrah, the crucial pilot-trained member of their team, remained seated and inconspicuous until after the cockpit was seized; and once inside, he would not have been visible to the passengers. 

Question: "When did Unit 93 drop?"

Response: "While travelling above eastern Ohio"
OPTIONS:
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A:
yes