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
Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things, which e
Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things, which e
admin
2011-02-08
76
问题
Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things, which exist on this planet for nearly 4, 000 million years. Do you know the size of bacteria? It can only be measured in microns. Maybe you have not a standard in your mind how long a micron is. One micron is a thousandth of a millimeter, which equals about the diameter of a pinhead. Therefore, even if we enlarged the rounded bacterium a thousand times, it would only be the size of a pinhead. We barely see bacteria by a magnification an ordinary microscope of 100 times, even if we try, we cannot make out anything of their structure. There are normally millions of them together, for they can multiply really fast.
Scientists have found that some bacteria have attached to wavy-looking "hairs" called flagella. The flagella rotate, pushing the bacteria through the water. Others can glide along over surfaces by some little-understood mechanism. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. They are active all the time. Even the bacteria without flagella often bound about in the water. They are pushed here and there,
colliding
with the watery molecules.
Bacteria cannot be detected because they don’t produce bad odor or change the color or texture of the food. Therefore, when people eat the food with many bacteria, they are likely to get hepatitis A, acute gastroenteritis and a host of other illnesses. Many households have refrigerators to prevent from bacteria. Of course, freezing food slows or stops-the growth of bacteria, however, when food is thawed, the bacteria will become reactivated. Bacteria can not be totally destroyed before the food is thoroughly cooked. We need to know that not all bacteria are in connection with illness. Just some bacteria can cause disease. They are called pathogenic bacteria. Fortunately our immune system can protect us from them.
Bacteria are prokaryotes (single cells that do not contain a nucleus). It may seem weird to classify organisms according to such details, but with or without a nucleus is not trivial at all. The division between prokaryotes and eukaryotes (all organisms with a nucleus inside their cells) is of extreme importance in biology, and is the result of a major evolutionary breakthrough. Visit our program tomorrow if you want to know more, thank you.
Which of the following ways can help people prevent from bacteria?
选项
A、Smell and have a careful look at the food.
B、Only eat the food stored in refrigerator.
C、Ensure the food is totally heated before eating.
D、Eat the food before they are thawed.
答案
C
解析
根据文章第三段第一句“Bacteria cannot be detected because they don’t produce bad odor or change the color…”可见,食物有没有细菌,只靠看或者是嗅是没有用的。A错误。根据本段第四句“Of course,freezing fbod slows or stops the growth of bacteria…”可见,冰箱里的食物其实也不一定安全,因为把食品冷冻可以放慢或使细菌停止生长,但不会彻底消灭细菌。B错误。根据本段倒数第四
转载请注明原文地址:https://kaotiyun.com/show/Emxd777K
本试题收录于:
公共英语四级笔试题库公共英语(PETS)分类
0
公共英语四级笔试
公共英语(PETS)
相关试题推荐
Readthefollowingstatementandwriteanessayonit.Inyouressay,youshould1)stateyouropinion,and2)supporti
Manypeoplewhoflyatleastoccasionallyhavecomedownwithacoldortheflushortlyafterdisembarking.Istheairinairbor
Manypeoplewhoflyatleastoccasionallyhavecomedownwithacoldortheflushortlyafterdisembarking.Istheairinairbor
Manypeoplewhoflyatleastoccasionallyhavecomedownwithacoldortheflushortlyafterdisembarking.Istheairinairbor
Societywasfascinatedbyscienceandthingsscientificinthenineteenthcentury.Greatbreakthroughsinengineering,theuseo
In1971therewereabout3,700millionpeopleintheworld.Ifthepopulationwere【C1】______evenlyovertheearth’ssurfacet
In1971therewereabout3,700millionpeopleintheworld.Ifthepopulationwere【C1】______evenlyovertheearth’ssurfacet
Whycan’tthelibraryissuelibrarycardstoeveryonewhoapplies?
随机试题
足月新生儿,第一胎,男,出生后第3天,母乳喂养,出生后24小时出现黄疸,皮肤黄染逐渐加重,查:Hb110g/L,母血型O,子血型B。遵医嘱给予该患儿光照治疗,光疗前的准备工作不包括
以下哪项不符合猫眼疮的临床表现:
A.渗出液B.漏出液C.介于渗出液与漏出液之间D.血性腹水E.乳糜腹水肝硬化腹水呈
患者,男,55岁,患者三天前自觉右胁背部疼痛,并逐渐出现疱疹,呈带状布,疼痛较剧,口干苦、大便干、小便黄,脉弦,舌红苔黄。根据病情应取哪组经络腧穴为主
定期租船合同的特点不包括()。
甲对乙享有50000元债权,已到清偿期限,但乙一直宣称无能力清偿欠款。甲调查发现,乙对丁享有3个月后到期的7000元债权,戊因赌博欠乙8000元;另外,乙在半年前发生交通事故,因事故中的人身伤害对丙享有10000元债权,因事故中的财产损失对丙享有5
下列关于土地增值税的表述中,正确的有()。
RAID级别是指磁盘阵列中硬盘的组合方式,不同级别的RAID为用户提供的磁盘阵列在性能上和安全性的表现上也有不同。图7-3是(50)磁盘阵列的工作原理示意图。
Weareanon-profitcompany______teammembersarefromalloverthecountry.
WhenLouiseBrownwasbornon25July1978,shekickedoffanera.Thefirst"testtubebaby"isamotherherselfnow,andshe’s
最新回复
(
0
)