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单项选择题

Please Fasten Your Seatbelts Severe turbulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局) engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it.
Clear-air turbulence often catches pilots by surprise. Invisible to radar, it is difficult to forecast and can hurl (用力抛出去) passengers about the cabin. In December 1997, one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 metres in a few seconds.
However, passengers can avoid serious injury by fastening their seatbelts. “It is the only antidote (对策) for this sort of things,” says Rod Bogue, project manager at NASA’s Dryden Flight Research Center in Edwards, California.
The centre’s new turbulence detector is based on lidar, or laser radar, Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane’s airspeed. But as the particles swirl (打漩) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity (激烈程度) of the turbulence.
In a series of tests that began last month, a research jet flew repeatedly into disturbed air over the mountain ridges (山脉) near Pueblo, Colorado. The lidar detector spotted turbulence between 3 and 8 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered.
Bogue says that he had “ a comfortable amount of time” to fasten his seatbelt. The researchers are planning to improve the lidar’s range with a more powerful beam. The system could be installed on commercial aircraft in the next few years.
第6题：What does “clear-air turbulence” probably mean? （Paragraph 1）
A．A not very rough storm.
B．Unexpected disturbed air.
C．A kind of visible storm.
D．A storm over mountain ridges.

A.
Clear-air
B.
However,
C.
The
D.
In
E.
Bogue
F.
第6题：What
G.A
H.Unexpected
I.A
J.A
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单项选择题 根据下列材料请回答 46～50 题：Bomb Explosions in ThailandThe new year celebration in Thailand was shattered by violence，when nine bombs exploded across Bangkok amend midnight．Three Thai citizens were killed and more than 30 injured．Among the injured，six were foreigners．No Chinese casualties were Chinese Embassy in Bangkok，the capital，said on Mondav. reported，the _______(46)But other embassies have advised their citizens to avoid traveling to Bangkok．'There is a possibility of further attacks in coming days，'said a travel advisory(公告)from Australia．'Australians are urged to avoid unnecessary travel in Bangkok．”No terrorist group claimed responsibility for the bombings by Tuesday _______(47)Bombings and shootings occur almost daily in Thailand's three，southernmost provinces．Yala，Naarathiwat and Battani have a dominant Muslim population and have long complained of neglect(忽视)and discrimination(歧视)in the largely Buddhist(佛教徒的)nation．They have asked for independence and a separate Islamic(伊斯兰的)state．Since 2004，the insurgents(叛乱者)have carried out numerous attacks in the south and more than 1，900 people have been killed________(48)But Thai P rime Minister Sprayed Chuluota said on Monday that domestic politics rather than the Muslim insurgency was behind the bombings．'It is likely related to people who lost their political benefits，'Sprayed said，referring to Tasking Chinaware．________(49)Sprayed was later appointed interim(临时的)prime minister Tasking，however still enjoys widespread support，especially in the countryside________(50)Tasking' s lawyer, Napped Patina，denied his client's involvement in the bombings，according to a local website. A．Nobody is to blameB．Some believe the explosions were the work of Muslim separatistsC．Some believe that several senior army officers loyal to Tasking plowed the bombings with ousted(赶下台)politicians to discredit(败坏名声)the government．D．Tasking was ousted in a military coup(政变)last SeptemberE．The Thai Government has been unable to control the violence，though thousands of troops have been sent to the south．F．The embassy issued no travel warnings 第 46 题 请选择（46）处最佳答案。

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