13．In its early history，Chicago had floods frequently，especially in the spring，making the streets so muddy that people，horses，and carts got stuck．An old joke that was popular at the time went something like this：A man is stuck up to his waist in a muddy Chicago street．Asked if he needs help，he replies，"No，thanks．I've got a good horse under me．"
The city planner decided to build an underground drainage （排水） system，but there simply wasn't enough difference between the height of the ground level and the water level．The only two options were to lower the Chicago River or raise the city．
An engineer named Ellis Chesbrough convinced the city that it had no choice but to build the pipes above ground and then cover them with dirt．This raised the level of the city's streets by as much as 12 feet．
This of course created a new problem：dirt practically buried the first floors of every building in Chicago．Building owners were faced with a choice：either change the first floors of their buildings into basements，and the second stories into main floors，or hoist the entire buildings to meet the new street level．Small wood-frame buildings could be lifted fairly easily．But what about large，heavy structures like Tremont Hotel，which was a six-story brick building？
That's where George Pullman came in．He had developed some house-moving skills successfully．To lift a big structure like the Tremont Hotel，Pullman would place thousands of jackscrews （螺旋千斤頂） beneath the building's foundation．One man was assigned to operate each section of roughly 10 jackscrews．At Pullman's signal each man turned his jackscrew the same amount at the same time，thereby raising the building slowly and evenly．Astonishingly，the Tremont Hotel stay open during the entire operation，and many of its guests didn't even notice anything was happening．Some people like to say that every problem has a solution．But in Chicago's early history，every engineering solution seemed to create a new problem．Now that Chicago's waste water was draining efficiently into the Chicago River，the ci ty's next step was to clean the polluted river．
29．The author mentions the joke to showB．
A．horses were fairly useful in Chicago
B．Chicago's streets were extremely muddy
C．Chicago was very dangerous in the spring
D．the Chicago people were particularly humorous
30．The city planners were convinced by Ellis Chesbrough toD．
A．get rid of the street dirt
B．lower the Chicago River
C．fight against heavy floods
D．build the pipes above ground
31．What can we conclude about the moving operation of the Tremont Hotel？A
A．It went on smoothly as intended．
B．It interrupted the business of the hotel．
C．It involved Pullman turning ten jackscrews．
D．It separated the building from its foundation．
分析 本文屬于說明文閱讀，作者通過這篇文章主要向我們描述了芝加哥城的問題和改造方案，他們因為洪水的經(jīng)常泛濫導(dǎo)致大街上總是泥濘不堪，但也已經(jīng)出臺了各種應(yīng)對政策．
解答 29．B．細節(jié)推理題．根據(jù)文章的第一段第一句話：In early history，Chicago had floors frequently，especially in the spring，making the streets so muddy that people，horses，and carts got stuck．可知芝加哥因為洪水的經(jīng)常泛濫導(dǎo)致大街上總是泥濘不堪，行人，馬和車全部都堵在路上．所以作者提及那個玩笑是為了突出芝加哥這一特點，故選B．
30．D．細節(jié)理解題．根據(jù)第三段第一句話：An engineer named Eill Chesbrough convinced the city that it had no choice but to build the pipes above ground and then cover thenwith dirt．可知以Eill Chesbrough為首的人們認為應(yīng)該在地上埋下排水管道，故選D．
31．A．細節(jié)推理題．根據(jù)倒數(shù)第二段中的倒數(shù)第二句話：At Pullman's signal each man turned his jackscrew the same amount at the same time，thereby raising the building slowly and evenly．（在Pullman的指導(dǎo)下，每個人同時抬起他們手中的千斤頂，因此建筑就被慢慢地、平整地抬起來了）可知A項正確，故選A．
點評 考察學生的細節(jié)理解和推理判斷能力，做細節(jié)理解題時一定要找到文章中的原句，和題干進行比較，再做出正確的選擇．在做推理判斷題不要以個人的主觀想象代替文章的事實，要根據(jù)文章事實進行合乎邏輯的推理判斷．
