首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
A、A bat caught the insect in midair and ate it. B、Dolphin’s clicking sounds bounced off the fish and back to it. C、A person hear
A、A bat caught the insect in midair and ate it. B、Dolphin’s clicking sounds bounced off the fish and back to it. C、A person hear
admin
2010-11-02
72
问题
Objects that are vibrating make sounds. Rhythmic sound vibrations produce sound waves which travel in every direction. The frequency of a sound is the number of waves that pass a given point each second. [29] The more rapid, an object vibrates, the greater the frequency of sound it makes. Frequency is measured in hertz. One hertz equals one sound wave per second. The frequency of sound determines the degree of highness or lowness of the sound. A high-pitched sound has a higher frequency than a low-pitched sound. [30] Humans hear sounds that have frequencies from about 20 hertz to 20,000 hertz. Sound with a frequency higher than 20,000 hertz is called ultrasound which is too high-pitched for humans to hear. However, many animals can hear ultra sound. Bats can hear higher sounds than any other animal. Some can hear up to 210,000 hertz. Bats send out lots of high-pitched squeaks and then listen to the echoes bouncing off things like insects. The shorter the time interval between the squeak and the echo, the closer they are to the insect. [31]Using sound to find or "see" things is called echolocation. Another animal that uses ultrasound is the dolphin. Dolphins can hear sounds up to about 150,000 hertz. Dolphins use sound waves to find food underwater. [31] They make clicking sounds that hit whatever is around them and then bounce back to the dolphins. Dolphins can send as many as 2,000 clicks per second. Dolphins’ ultrasound ability is so sensitive that they can detect small fish from l0 feet away.
选项
A、A bat caught the insect in midair and ate it.
B、Dolphin’s clicking sounds bounced off the fish and back to it.
C、A person heard an echo when he shouted into the valley.
D、A dog heard his owner’s whistle because he used ultrasound.
答案
B
解析
转载请注明原文地址:https://kaotiyun.com/show/HHs7777K
0
大学英语六级
相关试题推荐
A、Fuel-efficientcars.B、Airpollutioncausedbycars.C、HistoryofAutomobiledevelopments.D、Electric-poweredcars.D
Smartfirmscanminimizetheirrisksbyconductingweaknessappraisals,choosingexperiencedsecuritypersonnelandestablishin
Mostpeople’sjobsarelikelytobeeffectedbycomputers【S1】______inonewayorother.Teachers,forexample,canuse
OnemajordecisionwhichfacestheAmericanstudentreadytobeginhighereducationisthechoiceofattendingalargeuniversit
A、TheHydeparkCorner.B、TheLondonMuseum.C、KensingtonHighStreet.D、BakerStreet.B
Duringthe1990swewillwitnessmanytechnologicalchangesinthewaywecommunicate.Evenbooks,liketheoneyouarereading,
Lazinessisasin,everyoneknowsthat.Wehaveprobablyallhadlecturespointingoutthatlazinessis【B1】______,thatitisw
A、Lethimwinatennisgame.B、Helphimfinishhisanthropologyproject.C、Givehimsomemedicineforhisstomach.D、Lendhimhe
A、Theman’snervousbutbelieveshewillbebettertomorrow.B、Themanisbeggingthewomantolethimpassthepresentation.C、
A、Sheisgoingtoanexhibitionabroad.B、Sheisgoingtoaweddingceremony.C、SheisgoingonavoyageoverthePacific.D、She
随机试题
某女,22岁,腕、踝关节疼痛及脱发1年余,今晨郊游时发现面部出现紫红斑,遂就医。查体:头发稀疏,面颊及颈部均有不规则圆形红斑,口腔有溃疡。化验:血中查出狼疮细胞。病人返家后健康指导以下哪项不妥()
某男性,66岁,近日出现喘息、咳嗽、胸闷等症状,夜间及凌晨发作加重,呼吸较困难,并伴有哮鸣音。根据病情表现,该患者可能患有
张甲有两子张乙和张丙,因张乙和张丙在国外工作,无暇顾及张甲。张甲便与刘某签订一份遗赠扶养协议,将自己的房屋在死后赠与刘某,刘某尽生养死葬的义务。张甲在病危期间,张乙回到国内,张甲在临终前立下口头遗嘱,将其房屋由张乙继承(遗嘱符合形式要件)。张甲死亡后,王某
银行业监督管理机构的职责包括:()
关于单利和复利的区别,下列说法正确的是()。
以下哪种为社交礼仪中正确的介绍方式?()
职业是指劳动者为获得劳动报酬或收入所从事的社会劳动类别。职业具有哪些特征()。
公民年满16周岁并以自己的劳动收入为主要生活来源的,可以视为()。
CiscoPIX525防火墙可以进行操作系统映像更新的访问模式是()。
ThanksgivingDayisthemosttrulyAmericanofthenationalholidaysintheUnitedStatesandismostcloselyconnectedwiththe
最新回复
(
0
)