首页
登录
职称英语
What is the main topic of the passage? [br] [originaltext] What makes it
What is the main topic of the passage? [br] [originaltext] What makes it
游客
2024-10-24
18
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 ob-server, 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:http://tihaiku.com/zcyy/3815058.html
相关试题推荐
Nancybecameataxidriverbecause[originaltext]I:Hello,Nancy.Iknowyouare
Whatistheconversationmainlyabout?[br][originaltext]M:Whyareyoulookin
Japan’sdemandforimportslastmonth[br][originaltext]Japan’stradesur
Untilwhattimewillthetornadowatchbeineffect?[originaltext]Weinter
Thesepeoplewerearrestedfor_______.[originaltext]TheIranianauthoriti
Whatisthemaintopicofthepassage?[br][originaltext]Whatmakesit
Whatisthemaintopicofthepassage?[br][originaltext]Whatmakesit
Whatisthemaintopicofthepassage?[originaltext]Whatmakesitrain?
Whatisthestudent’sproblem?[br][originaltext]M:Thisbookisduetoday,bu
Whatisthestudent’sproblem?[br][originaltext]M:Thisbookisduetoday,bu
随机试题
Activelearningoccurswhenalearnertakessomeresponsibilityforthedevel
Organicfarmershadfoughttopreventgenetically-engineeredcropsfrombein
UnitedNations(UN)isaninternational【C1】______ofcountriescreatedto【C2】
对《程序文件》的审查要点包括()。A.需要有程序文件描述的要素,均被恰当地
A.分泌物增多,无或轻度瘙痒,阴道黏膜正常 B.重度瘙痒,灼烧感,阴道黏膜水肿
患儿,女,3岁,麻疹恢复期,体温突然再次升高,伴嗜睡、惊厥等症状,护士应考虑该患
某企业以临时性流动负债来满足全部临时性流动资产和部分永久性资产的需要,而余下的永
缓解类风湿病患儿早期症状的主要药物是A:类固醇激素 B:非甾体类抗炎药 C:
下列选项中,属于真武汤原方加减法的是 A.腹痛者,倍芍药,加炙甘草B.下利者
理财师的专业能力即投资理财产品选择、组合和理财规划的能力。()
最新回复
(
0
)