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
55
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
Packagingisthedesignandproductionofphysicalcontainerforaproduct,whichinfactbecomesapartoftotalutilityofthe
Theterm"LearningDisabilities"meansadisorderinoneormoreofthebasicpsychologicalprocessesinvolvedinunderstanding
A、Theymayfinditdifficulttoinflatetheirballoons.B、Theirballoonsarepotentiallyexplosiveanddangerous.C、Theirflight
A、Basketballandvolleyball.B、Swimmingandtennis.C、Fittingtrainingandswimming.D、Weight-liftingandtennis.C
A、TalktoDr.Smithabouttheproblem.B、Studyharderforthenextbiologytest.C、Findouthoweveryoneelsedidonthetest.D
Menseemtohavealwaystakenaninterestinmeteorites,butnotuntiltheearlynineteenthcenturyweretheseobjectsconsidere
Directions:Forthispart,youareallowedthirtyminutestowriteashortessayentitledOnBuyingSecondhandTextbooks.Yous
Mostpeople’sjobsarelikelytobeeffectedbycomputers【S1】______inonewayorother.Teachers,forexample,canuse
Mostpeople’sjobsarelikelytobeeffectedbycomputers【S1】______inonewayorother.Teachers,forexample,canuse
Inmanaginginformationresources,themediummaybethekeytoaneffectivesystem.Themediumisavehicle,atool,oraconta
随机试题
设f具有二阶连续偏导数,u=f(x,xy,xyz),则=______。
指药物在中枢神经系统产生的一种特殊的精神效应,患者有一种强烈渴求用药的意念,使其不顾一切地去寻求药物以满足自己的欲望,称为
诊断应考虑为该病人手术后,下列哪一项不可能出现
A.腹膜炎出现早B.腹膜炎严重,呈板状腹C.腹膜炎出现较晚,但较重D.腹膜炎出现较晚且较轻E.无腹膜刺激征胰腺损伤的临床特征是
属于隐蔽抗原的物质是
心主神志的物质基础是
患儿,6岁。发热3天,口腔内黏膜、齿龈溃烂,周围掀红,疼痛拒食,舌质红、苔薄黄。其诊断是()
汇总记账凭证账务处理程序的缺点有()。
关于保证贷款中借款合同和保证合同的签订,以下说法错误的是()。
在选择确定项目的投资机遇中,()是将项目意向变为概略的投资建议。
最新回复
(
0
)