题目

4.8除以2.3加上1.8乘0.5的积，商是（）A. 1.7B. 44.88C. 3.2D. 1.5 答案：【答案】D【解析】根据题意，先求出1.8乘0.5的积，再加上2.3并求出它们的和，然后再用4.8除以它们的和即可。4.8÷(2.3+1.8×0.5)=4.8÷(2.3+0.9)=4.8÷3.2=1.5故答案为：D。 Louis Pasteur, the famous French chemist and bacteriologist(微生物学家), invented “pasteurization”. In 1854 Pasteur was made head of the department of science at the University of Lille, and it was there that he made one of his most famous discoveries. Lille was a major center for wine and beer-making, and some of the local wine-makers asked Pasteur if he could help solve the problem of keeping wine fresh. At that time, it was believed that food and drinks go “bad” due to a purely chemical process. But during a series of experiments Pasteur proved that tiny living organisms(微生物)caused food and drinks to go bad. In the case of wine and beer the organisms are already present in the form of the various yeasts (酵母) that caused the fermentation(发酵) process. Pasteur discovered that heating the wine gently for a few minutes after it had fermented would kill off the yeast that was left in the wine, with the result that the wine would remain fresh for much longer. He also proved that food and drinks could be turned bad by other organisms that were present in the air, and that they too would keep fresh much longer if they were kept in airtight containers. The heating process was so successful that it made Pasteur famous. It was named “pasteurization” in his honour, and by about 1900 it had been widely used for processing and bottling cows’ milk. The result was a huge drop in the number of bottle-fed babies dying from infant diarrhea(婴儿腹泻)and from that time on it has been a standard treatment for milk and many other food products. This simple process has saved thousands, possibly millions, of lives worldwide. 1.Pasteur became ___________ in 1854. A. the chairperson of the science department at the University of LilleB. the director of a chemical laboratory at the University of LilleC. the general manager of a large beer-making companyD. the president of the University of Lille2.According to the passage, Lille was a major center for ___________ in the mid-19th century. A. growing grain crops B. making beer and wineC. doing chemical research D. producing various kinds of yeasts3.In the last sentence of Paragraph 1, the underlined word “they” refers to ___________. A. wine and beerB. food and drinks C. the various yeastsD. other organisms4.We can infer from the passage that Pasteur’s discovery __________. A. is no longer widely used for treating milk and other food productsB. did not bring much profit to the wine makers in LilleC. has done a lot of good to children in the worldD. has greatly reduced the number of wars in the world5.According to the passage, we know it is that causes food and drinks to go bad.A. a purely chemical process. B. tiny living organisms(微生物)C. keeping them in airtight containers. D. the heating process