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（请给出正确答案）
A.地球和这两颗行星的大小不同
B. 这两颗行星上没有能生成有机物的物质存在
C. 地球和这两颗行星生成的时间不同
D. 这两颗行星距地球很远，不可能有生物存在
答案
更多“美国国家航空航天局（NASA）的美国天文学家正式宣布，他们发现了太阳系外的两颗小行星，与人”相关的问题
第2题
第5题
A.太空藻种：源自美国航天局NASA太空项目
B.含量高纯：纯DHA含量最高达200mg
C.全球首款：1997年全球首款DHA营养品
D.专注智慧：专注大脑智慧营养开发
第6题
A.2014 年 9 月，印度曼加里安号火星探测器（MOM）顺利抵达火星，进入环绕火星的轨道
B.曙光号探测器在本月抵达谷神星，在此之前它已对灶神星进行过相关探测
C.甚大望远镜（VLT）、凯克望远镜（Keck）、郭守敬望远镜（LAMOST）和盖亚望远镜（GAIA） 都是地基望远镜
D.美国航空航天局的 MAVEN 探测器是专门用于研究火星大气的设备
第7题
A.目前航空航天研究项目的预算经费越来越高
B.国会的决议影响了美国的航空航天局新项目的开展
C.对于火星上是否有生命的研究未来可能难以为继
D.预算压力将成为美国大型航天项目被叫停的主要原因
第8题
根据下列材料，请回答题
Please Fasten Your Seatbelts
Severe turbulence （潮流 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 fore- cast 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 meters 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 thing，" 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 kilometers 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.
What does "clear-air turbulence" in Paragraph 1 probably mean？ 查看材料
A.A not very rough storm.
B.Unexpected disturbed air.
C.A kind of visible storm.
D.A storm over mountain ridges.
