Questions 91 to 100 are based on the following passage.
【真题来源：2018年12月大学英语四级真题（第三套）Part Ⅲ，Section B，第11-20题】
Is It really OK to eat food that's fallen on the floor?
A) When you drop a piece of food on the floor, is it really OK to eat if you pick it up within five seconds? An food myth contends that if food spends just a few seconds on the floor, dirt and germs won't have much chance to contaminate it. Research in my lab has focused on how food becomes contaminated, and we've done some work on this particular piece of wisdom.
B) While the ‘five-second rule’ might not seem like the most pressing issue for food scientists to get to the bottom of, it's still worth investigating food myths like this one because they shape our beliefs about when food is safe to eat.
C) So is five seconds on the floor the critical threshold（门槛）that separates a piece of eatable food from a case of food poisoning? It's a bit more complicated than that. It depends on just how many bacteria can make it from floor to food in a few seconds and just how dirty the floor is.
D) Wondering is food is still OK to eat after it's dropped on the floor is a pretty common experience. And it's probably not a new one either. A well-known, but inaccurate, story about Julia Child may have contributed to this food myth. Some viewers of her cooking show, The French Chef, insist they saw Child drop lamb on the floor and pick it up, with the advice that if they were alone in the kitchen, their guests would never know.
E) In fact it was a potato pancake, and it fell on the stovestop, not on the floor. Child put it back in the pan, saying, “But you can always pick it up and if you're alone in the kitchen, who's going to see it?” But the misremembered story persists. It's harder to pin down the origins of the oft-quoted five-second rule, but a 2003 study reported that 70% of women were more likely than men to eat food that had dropped on the floor.
F) So what does science tell us about what a few moments on the floor means for the safety of your food? The earliest research report on the five-second rule is attributed to Jillian Clarke, a high school student participating in a research project at the University of Illinois. Clark and her colleagues introduced bacteria transferred from the tiles to the cookies on the tiles for varying times. They reported bacteria were transferred from the tiles to the cookies within five seconds, but didn't report the specific amount of bacteria that made it from the tiles to the food.
G) But how many bacteria actually transfer in five seconds? In 2007, my lab at Clemson University published a study in the Journal of Applied Microbiology. We wanted to know if the length of time food is in contact with a contaminated surface affected the rate of transfer of bacteria to the food. To find out, we introduced bacteria to squares of tile, carpet or wood. Five minutes after that, we placed either bacon or bread on the surface for 5, 30 or 60 seconds, and then measured the number of bacteria transferred to the food. We repeated this exact procedure after the bacteria had been on the surface for 2,4,8 and 24 hours.
H) We found that the number of bacteria transferred to either kind of food didn't depend much on how long the food was in contact with the contaminated surface — whether for a few seconds or for a whole minute. The overall number of bacteria on the surface mattered more, and this decreased over time after the initial introduction. It looks like what's at issue is less how long your food stays on the floor and much more how contaminated with bacteria that patch of floor happens to be.
I) We also found that the kind of surface made a difference as well. Carpets, for instance, seem to be slightly better places to drop your food than wood or tile. When a carpet was contaminated, less than 1% of the bacteria were transferred. But when the food was in contact with tile or wood, 48 - 70% of bacteria were.
J) Last year, a study from Aston University in the UK used nearly identical parameters（参数）to our study and found similar results. They also reported that 87% of people asked either would eat or had eaten food fallen on the floor.
K) Should you eat food fallen on the floor then? From a food safety standpoint, if you have millions or more bacteria on a surface, 0.1% is still enough to make you sick. Also, certain types of bacteria are extremely harmful, and it takes only a small number to make you sick. For example, 10 bacteria or less of an especially deadly strain of bacteria can cause severe illness and death in people with compromised immune systems. But the chance of these bacteria being on most surfaces is very low.
L) And it's not just dropping food on the floor that can lead to bacterial contamination. Bacteria are carried by various ‘media’, which can include raw food, moist surfaces where bacteria have been left, our hands or skin and from coughing or sneezing（打喷嚏）. Hands, foods and utensils（器皿）can carry individual bacteria living in communities contained within a protective film. These microscopic layers of deposits containing bacteria are known as biofilms and they are found on most surfaces and objects. Biofilm communities can harbor bacteria longer and are very difficult to clean. Bacteria in these communities also have an enhanced resistance to sanitizers（清洁剂）and antibiotics compared to bacteria living on their own.
M) So the next time you consider eating fallen food, the odds are in your favor that you can eat it without getting sick. But in the rare chance that there is a micro-organism that can make you sick on the exact spot where the food dropped, you can be fairly sure that the bug is on the food you are about to put in your mouth.
N) Research or common sense tells us that the best thing to do is keep your hands, utensils and other surfaces clean.
A research project found bacteria made their way to the food on the floor in five seconds.
根据题目中的A research project和in five seconds可查找到F段。根据F段第2句和最后一句可知，最早关于“五秒定律”的研究报告来自于一位参加伊利诺伊大学研究项目的高中生；该名高中生和其伙伴的研究报告称，细菌在五秒钟之内就从实验用的瓷砖转移到了饼干上。题目复现了文章原词a research project，其中的made their way to是原文were transferred from...to...的同义替换，in five seconds与within five seconds同义。F段为本题信息出处。
Whether food is contaminated depends much on the number of bacteria that get onto it.
本题考查食物受污染与否的主要决定因素。根据题目中的the number of bacteria that get onto it可查找到C段。该段首句提出问题：食物掉地上的这五秒钟真的是决定其可继续食用还是受到了污染的门槛吗?该段最后一句提到，这取决于有多少细菌可以在几秒之内从地板转移到食物上，以及地板有多脏。题目中的whether food is contaminated与C段首句中的the critical threshold that separates a piece of eatable food from a case of food poisoning对应(食物eatable相当于未受污染，poisoning即已受污染)，the number of bacteria that get onto it与原文how many bacteria can make it from floor to food相符。C段为本题信息出处。
H段首句出现了题目原词depend much on以及the number of bacteria transferred to...food等字眼。但联系前后文可知，该段是前一段study“课题”的研究发现，主要回答G段中“食物与受污染表面接触的时间长短是否会影响细菌转移的数量(if the length of time...affected the rate of transfer of bacteria to the food)”这一问题，而题目探讨的“食物是否受污染”与“转移至食物上的细菌数量”之间的关系未在该段提及。
Food contamination may result from various factors other than food dropping on the floor.
Males are less likely than females to eat food that may have been contaminated.
根据Males和females以及eat food that may have been contaminated可查找到E段最后一句。该句后半部分提到，相比男性，女性更有可能吃掉在地上的食物。题目是对该信息的正话，反说，其中Males和females是对原文men和women的同义替换，food that may have been contaminated是原文food that had dropped on the floor的同义替换。E段为本题信息出处。
The author's research centers around how food gets contaminated.
根据The author's research和centers around可查找到A段。该段最后一句提到，作者在实验室的研究专注于研究食物是如何被污染的。题目中的The author's research是原文Research in my lab的同义替换，centers around是原文focused on的同义替换，how food gets contaminated与原文中的how food becomes contaminated对应。A段为本题信息出处。
Keeping everything clean is the best way to stay healthy.
根据Keeping everything clean和the best way可查找到N段。该段提到，研究和常识告诉我们，最好的做法就是保持双手、器皿和其他表面清洁。题目中的stay healthy是对原文的合理推断，Keeping everything clean是对原文keep your hands, utensils and other surfaces clean的概括，the best way是the best thing的同义替换。N段为本题信息出处。
Chances are you will not fall sick because of eating food picked up from the floor.
根据题目中的Chances和will not fall sick可查找到M段。该段首句提到，考虑吃掉在地上的食物时，很有可能吃下去后不会生病。题目中的Chances are (that)...是一个固定句型，表示“很有可能……”，与原文the odds are in your favor表述相符，food picked up from the floor是原文fallen food的同义替换，will not fall sick对应原文without getting sick。M段为本题信息出处。
For a long time people have had the experience of deciding whether or not to eat food picked up from the floor.
根据have had the experience和deciding whether or not to eat可查找到D段前两句。这两句话说的是，想知道食物掉在地上之后还能不能吃是一种很常见的经历，而且这可能也不是什么新鲜事。题目中的For a long time people have had the experience是对原文a pretty common experience和not a new one的概括，deciding whether or not to eat food是对原文wondering if food is still OK to eat的同义改写，picked up from the floor与原文dropped on the floor对应。D段为本题信息出处。
Some strains of bacteria are so harmful that a tiny few can have deadly consequences.
根据strains of bacteria, harmful, a tiny few和deadly consequences可查找到K段第3～4句。该段第3句提到，某些类型的细菌的危害极大，少量就能致病。随后第4句补充提到一种特别致命的细菌的10个或更少的菌株，就能使免疫系统受损的人得重病或者死亡。题目中的strains of bacteria与原文的certain types of bacteria和strain of bacteria对应，so harmful与原文extremely harmful同义，a tiny few与原文a small number和10 bacteria or less对应，have deadly consequences是对原文cause severe illness and death的概括。K段为本题信息出处。
Researchers found how many bacteria got onto the food did not have much to do with how long the food stayed on a contaminated floor.
根据题目中的did not have much to do with和how long the food stayed...可查找到H段。该段首句提到，转移至每种食物的细菌数量和食物接触受污染表面的时长并没有太大关系。题目中的how many bacteria与原文the number of bacteria意思一致，got onto the food与原文transferred to either kind of food对应，did not have much to do with是原文didn't depend much on的同义替换，stayed on是原文was in contact with的同义替换，a contaminated floor与原文the contaminated surface对应。H段为本题信息出处。