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问题 选择题

在2008年北京奥运会上，跳水运动员陈若琳取得了女子10米跳台的金牌．假设她的质量为m，进入水后受到水的阻力而做匀减速运动，设水对她的阻力大小恒为F，那么在她减速下降h的过程中，下列说法正确的是（　　）

A．她的动能减少了Fh

B．她的机械能减少了Fh

C．她的机械能减少了（F-mg）h

D．她的重力势能增加了mgh

答案

A、运动员下降的过程中，受到重力和阻力作用，根据动能定理，动能增加量等于（mg-F）h，故A错误；

B、C：除重力外的各个力做的总功等于机械能的增加量，除重力外，运动员克服阻力做功为Fh，故机械能减小Fh．故B正确、C错误．

D、重力做功为mgh，重力做功等于重力势能的减小量，故重力势能减小mgh，故D错误．

故选B．

完形填空
John Snow was born and worked as a __36__ in Great Britain．Exactly, he was an anaesthetist，37 means that he put people to sleep during operation．He also began to experiment using the same drugs to help women when they had   38 ．That is why he became the doctor who  39 Queen victoria to give the birth of her babies．
At the time he lived，cholera was the most  40 disease．Neither its cause，nor its  41 was understood．So many thousands of people died  42 there was an outbreak．John Snow was  43 to help ordinary people   44  from cholera．He  45  the disease began in the stomach and the patients died quickly after severe vomiting(呕吐)and diarrhea (腹泄)．46 ，he believed cholera resulted from water．When another  47 hit London in 1854，John Snow set to work．
John Snow approached the problem in a systematic way．He marked on a map  48 all the dead people had lived and found many of the   49  were near a water pump．It seemed the water was the 50 ．So he collected information about the  51 habits of the dead people and used them eventually to prove his theory．With the information  52  ，John Snow was sure  that   53  water was the cause．
Then people were required to 54  the water company to supply them with clean water．Thanks __55___ John Snow there was no more outbreaks of cholera．
小题1:
A．scientistB．an officialC．an officerD．doctor
小题2:A．who           B．that          C which        D．it
小题3:
A．painB．acheC．difficultiesD．babies
小题4:
A．assisted withB．took careC．look afterD．joined
小题5:
A．surprisingB．interestingC．interestedD．frightening
小题6:
A．cureB．methodC．resultD．threat
小题7:
A．each timeB．at one timeC．in no timeD．the first time
小题8:
A．delightedB．devotedC．absorbedD．determined
小题9:
A．sufferedB．having sufferedC．sufferingD．being suffered
小题10:
A．noticedB．was noticingC．has noticedD．had noticed
小题11:
A．ThereforeB．As a result ofC．SoD．According to
小题12:
A．diseaseB．disasterC．outbreakD．case
小题13:
A．howB．whereC．whatD．in which
小题14:
A．womenB．menC．deathD．injuries
小题15:
A．resultB．causeC．originD．case
小题16:
A．drinkingB．1ivingC．workingD．housing
小题17:
A．having collectedB．being collectedC．collectedD．collecting
小题18:
A．being pollutedB．pollutedC．pollutingD．having polluted
小题19:
A．take onB．call onC．depend onD．carry on
小题20:
A．toB．/C．forD．on
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单项选择题

临床上放射免疫分析最常用的放射性核素为（）

A．130I

B．125I

C．3H

D．14C

E．51Cr
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