2021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 DatingNowadays 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.The half - life of C - 14 is about 25 ,000 years.【单选题】

A.Right

B.Wrong

C.Not mentioned

正确答案:C

答案解析:本题有较大难度，答案依据不明显，需要通读全文作出判断。通读全文后可以发现文章并未提及碳的半衰期是25，000年，所以本题是未提及的，答案是C。

2、Walking to Exercise the BrainDo you think sitting and studying all the time will improve students grades? Think again. Getting some exercise may help, too.New research with older people suggests that taking regular walks helps them pay attention better than if they didn\'t exercise.Previous research had shown that mice learn, remember and pay attention better after a few weeks of working out on a running wheel. Mice that exercise have greater blood flow to the brain than those who don\'t. Their brain cells also make more connections.Neuroscientists (神经科学家) from the University of Illinois at Urbana Champaign wanted to find out if the same thing is true for people. First, they measured the physical fitness of 41 adults, ages 58 to 77, after each person walked I mile. Then, participants looked at arrows on a computer screen and had to use computer keys to show which way one particular arrow was pointing.Adults who were physically fit were faster at the arrow task, and their answers were just as accurate as their less - fit peers, the researchers found. The fitter participants also had more blood flow to a part of their brain responsible for paying attention and making decisions.In a second study, 15 elderly people who completed a 6 - month aerobic - training (有氧运动) course were faster at attention tasks compared with 14 seniors who just did stretching and toning (韵律操) exercises for the same amount of time.So, even going for a walk every 2 or 3 days for just 10 to 45 minutes can help. That should be good news for the elderly.The effects of exercising on the brains of younger people haven\'t been studied yet. Still, it can\'t hurt to take occasional breaks and go for a walk or run around with friends. Whatever you do, though, don\'t try to read and walk at the same time. You could end up hurting yourself!The first study on 41 elderly people found ______.【单选题】

A.the less - fit participants did arrow tasks faster

B.the fitter participants did arrow tasks faster

C.the less - fit participants gave more accurate answers

D.the fitter participants gave more accurate answers

正确答案:B

答案解析:本题有一定难度，需要认真阅读文章。答案依据在文章第五段。带着题干信息词回到文章定位。第五段第一句谈到，研究者发现身体健康的成年人完成箭头测试的速度更快，回来看选项，很明显，B是近义解释，是答案。

3、The company recommended that a new petrol station should be built here. 【单选题】

A.ordered

B.insisted

C.suggested

D.demanded

正确答案:C

答案解析:recommend:推荐；order:命令；insist:坚持；suggest:建议；demand：要求。只有suggest与recommend语义相近，所以答案为C。

4、His shoes were shined to perfection.【单选题】

A.cleared

B.polished

C.washed

D.mended

正确答案:B

答案解析:他的鞋被擦得铮亮。本题难度不大，干扰项干扰不明显。查词典，找到shine的引申意思“擦亮”，选项里只有polish有擦亮鞋的意思，所以确定答案不难，本题是送分题。

5、Jack packed up all the things he had accumulated over the last ten years.【单选题】

A.future

B.far

C.past

D.near

正确答案:C

答案解析:杰克把过去10年里攒的所有东西都收拾好打行李了。本题难度不大，干扰项干扰不强，是送分题。last和past都指“过去的”是同义词，最佳答案是C。