2020年职称英语考试《理工类》考试共65题，分为单选题和多选题和判断题和计算题和简答题和不定项。小编每天为您准备了5道每日一练题目（附答案解析），一步一步陪你备考，每一次练习的成功，都会淋漓尽致的反映在分数上。一起加油前行。

1、Radiocarbon Dating
Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射性碳), or carbon - 14 dating. One key to understanding how and why something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon -12, has six protons (质子) and six neutrons (中子) in its nucleus (原子核). Carbon - 14, or C - 14, is a radioactive, unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay (衰减). This process involves the loss of the extra neutrons and energy from the nucleus.
In Libby's radiocarbon dating technique, the weak radioactive emissions(放射)from this decay process are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C -14 atoms in the sample being dated.
Carbon - 14 is produced in the Earth's atmosphere when nitrogen(氮) - 14, or N - 14, interacts with cosmic rays (宇宙射线). Scientists believe since the Earth was formed, the amount of nitrogen in the atmosphere has remained constant. Consequently, C -14 formation is thought to occur at a constant rate. Now the ratio of C -14 to other carbon atoms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years.
All life on Earth is made of organic molecules (分子) that contain carbon atoms coming from the atmosphere. So all living things have about the same ratio of C -14 atoms to other carbon atoms in their tissues (组织). Once an organism (有机体) dies it stops taking in carbon in any form, and the C -14 already present begins to decay. Over time the amount of C - 14 in the material decreases and the ratio of C - 14 to other carbon atoms goes down. In terms of radiocarbon dating, the fewer C -14 atoms in a sample, the older that sample is.
When an organism dies, the C -14 in it begins to decay.
【单选题】

A.Right

B.Wrong

C.Not mentioned

正确答案:A

答案解析:本题有一定难度，但答案依据比较明显。带着题干信息词回文章定位，文章最后一段第三句：Once an organism dies it stops taking in carbon in any form，and the C - 14 already present begins to decay谈到一旦有机体死亡，就停止吸收任何形式的碳，现有的碳14也会逐渐衰变，题干是其近义解释，所以正确，答案是A。

2、Seeing Red Means Danger Ahead
The color red often means danger and by paying attention, accidents can be prevented. In the future, the color red also may help prevent danger at construction sites. Thanks to new work by engineers, bridge supports or other kinds of materials, could one day contain a color - changing material. It will turn red before a structure collapses or falls apart.
The secret behind the color - changing material is a particular type of molecule (分子). A molecule is a group of atoms (原子) held together by chemical bonds. Molecules come in all shapes and sizes and make up everything you can see, touch or feel. How a molecule behaves depends on what kinds of atoms it contains and how they're held together.
When a polymer (聚合物) containing a color - changing molecule called a mechanophore (机械响应性聚合物) is about to break, it produces a color. When a polymer with mechanophore molecules becomes "injured" or weak, one of the mechanophore bonds breaks and the material turns red. "It's a really simple detection method," says Nancy Sottos, one of the scientists who worked on the project. Sottos and her team tested the color - changing polymers in their lab. The test results proved encouraging.
There is a way to get rid of the red color light. When a bright light is shone on the mechanophore, the broken bond is fixed and the red color disappears. Thus "self - healing" may be a problem for engineers. They need to use the color - changer in big construction projects that will be outside, under sunlight. And sunlight will make the mechanophore's warning system useless.
Sottos and her fellow scientists still have _____ work to do before the color - changing molecules can be used outside the lab.
【单选题】

A.a pair of

B.a type of

C.a lot of

D.a part of

正确答案:C

答案解析:本题难度不大，考查词义辨析。文章此处是说“Sottos和同事们还有很多工作要做”，答案是C。

3、Better Control of TB Seen if a Faster Cure is Found
The World Health Organization estimates that about one-third of all people are infected with bacteria that cause tuberculosis. Most times, the infection remains inactive. But each year about eight million people develop active cases of TB, usually in their ______. Two million people die of it. The disease has increased with the spread of AIDS and drug-resistant forms of tuberculosis.
Current treatments take at least six months. Patients have to take a combination of several antibiotic drugs daily. But many people stop as soon as they feel better. Doing that can lead to an infection that resists treatment. Public health experts agree that a faster-acting cure for tuberculosis would be more effective. Now a study estimates just how effective it might be. A professor of international health at Harvard University led the study. Joshua Salomon says a shorter treatment program would likely mean not just more patients cured. It would also mean fewer infectious patients who can pass on their infection to others.
The researchers developed a mathematical model to examine the effects of a two-month treatment plan. They tested the model with current TB conditions in Southeast Asia. The scientists found that a two-month treatment could prevent about twenty percent of new cases. And it might prevent about twenty-five percent of TB deaths. The model shows that these reductions would take place between two thousand twelve and two thousand thirty. That is, if a faster cure is developed and in wide use by two thousand twelve.
The World Health Organization developed the DOTS program in nineteen ninety. DOTS is Directly Observed Treatment, Short-course. Health workers watch tuberculosis patients take their daily pills to make sure they continue treatment.
Earlier this year, an international partnership of organizations announced a plan to expand the DOTS program. The ten-year plan also aims to finance research into new TB drugs. The four most common drugs used now are more than forty years old. The Global Alliance for TB Drug Development says its long-term goal is a treatment that could work in as few as ten doses.
【单选题】

A.kidneys

B.lungs

C.bones

D.livers

正确答案:B

答案解析:结核病多发于肺部，这是一般的常识。

4、English and English Community
1 There is no doubt that English is a useful language. The people who speak English today make up the largest speech community in the world with the exception of speakers of Chinese.
2 A speech community is similar to other kinds of communities. The people who make up the community share a common language. Often they live side by side, as they do in a neighborhood, a village, or a city. More often they form a whole country. National boundaries, however, are not always the same as the boundaries of a speech community. A speech community is any group of people who speak the same language no matter where they happen to live.
3 We may say that anyone who speaks English belongs to the English speech community. For convenience, we may divide the speakers into two groups: one in which the speakers use English as their native language, the other in which the speakers learn English as a second language for the purpose of education, commerce, and so on.
4 Learning a second language extends one's vision and expands the mind. The history and literature of a second language record the real and fictional lives of people and their culture; a knowledge of them adds to our ability to understand and to feel as they feel. Learning English as a
second language provides another means of communication through which the window of the entire English speech community becomes a part of our heritage.
People who live in different places may belong to____.
【单选题】

A.a second language

B.the same language

C.the same speech community

D.any other language

E.national boundaries

F.a part ofone's heritage

正确答案:C

答案解析:从文章第2段可知，居住在不同地区的人们有可能同属一个speech community。

5、We have got to abide by the rules. 【单选题】

A.stick to

B.persist in

C.safeguard

D.apply

正确答案:A

答案解析:abideby和stick to同义，遵循；persist in:坚持；safeguard：保护；apply：应用、申请。