首页
登录
职称英语
What is the main topic of the passage? [br] [originaltext] What makes it ra
What is the main topic of the passage? [br] [originaltext] What makes it ra
游客
2023-11-22
49
管理
问题
What is the main topic of the passage? [br]
What makes it rain? Rain falls from clouds for the same reason anything falls to Earth. The Earth’s gravity pulls it. But every cloud is made of water droplets or ice crystals. Why doesn’t rain or snow fall constantly from all clouds? The droplets or ice crystals in clouds are exceedingly small. The effect of gravity on them is minute. Air currents move and lift droplets so that the net downward displacement is zero, even though the droplets are in constant motion.
Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight. To the casual observer, dust seems to act in a totally random fashion, moving about chaotically without fixed direction. But in fact dust particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that it would take sixteen hours to fall a mile in perfectly still air, and it does not fall out of moving air at all. Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of a cloud droplet to a size large enough to fall out is the cause of rain and other forms of precipitation. This important growth process is called "coalescence".
选项
A、They are balanced by the pressure of rain droplets.
B、The effect of gravity at high altitude is random.
C、They are kept in the sky by air current.
D、They are moving about with fixed direction.
答案
C
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3209117.html
相关试题推荐
Thearticlewouldmostlikelybefoundin______[br][originaltext]Ifyour
Themainpurposeoftheresearchis______[br][originaltext]W:Excuseme,cou
Themainpurposeoftheresearchis______[br][originaltext]W:Excuseme,cou
Thewomanisinterestedinseeing______[br][originaltext]M:Areyoureadyfo
Thewomanisinterestedinseeing______[br][originaltext]M:Areyoureadyfo
Thewomanisinterestedinseeing______[originaltext]M:Areyoureadyforthe
[originaltext]Asickorinjuredpersoncanobtainmedicalcareinseveral
Howmanypeoplewerekilledinthebombingaltogether?[originaltext]It’s
Whatisthemainconcernoftalk?[br][originaltext]TodayIwouldliketo
Whathappenstotreeseachyear?[br][originaltext]Duringthiscentury,a
随机试题
AccordingtoWorldHealthOrganization,howmanypeopleamkilledbyoutdoorair
[originaltext]M:CanyoubelievewhatCarolsaidwhenProfessorFranklinasked
我国传统教育单纯采用交流式教育方法。()
事先不规定抽样次数,每次只抽一个单位产品,即样本量为1,据累积不合格品数判定批合
下列()等应列入建筑安装工程直接工程费的人工费。A.生产工人劳动保护费 B
甲地公民刘某不服乙地铁路公安局的处罚决定,分别向甲地基层人民法院和乙地铁路运输法
共用题干 (一)资料张某、王某、李某三人商定出资100万元设立甲科技开发有限责
(2018年)下列所得,可享受企业所得税减半征收优惠的是( )。A.种植油料作物
负责医疗机构药品质量管理工作的是A.药库 B.药检室 C.质控办 D.药事
按投资时间长短,无形资产投资属于( )。 A.短期投资 B.长期投资
最新回复
(
0
)