某男，51岁，．缺失，5年前曾在诊所行单端固定桥修复，现诉：松动疼痛检查，锤造开面冠，作为单端固定桥的固位体。开面冠边缘与颈缘有间隙。牙龈区红肿，探诊易出血。Ⅰ～Ⅱ度松动，叩(+)。

松动的主要原因

A:制作不当 B:设计不当 C:固位体与基牙不密合 D:牙龈炎的表现 E:牙髓炎的表现

对4种食品抽样进行真菌检验，结果如下表所示：

用χ检验比较4种食品的真菌检出率，宜选用的公式是

A: B: C: D: E:

对4种食品抽样进行真菌检验，结果如下表所示：

用χ检验比较4种食品的真菌检出率，宜选用的公式是

A: B: C: D: E:

The Magic of Sound

Music is one of the most beautiful forms of artistic expressions ever invented. In movies and plays, music has an added function¹: it not only moves people but also can shock people. Is it true that an ordinary musical instrument can be so powerful?

Our eardrums can withstand sound within 20 to 80 decibels. Once sound exceeds this limit², even beautiful music will become car-splitting noise³ and harm health. A strong blast of high sound can twist and break a solid iron sheet.   1   

The noise from a plane’s engine is over 140 decibels. However, the sound of a flute is at most a few decibels.    2    It has been proven that people who have worked in an environment with a high sound intensity for a long time suffer varying degrees of heart disease or altered brain waves.

In movies, sometimes the hero can produce a sound that ordinary people can’t hear and only those who have the same ability can feel. In nature, there is actually sound that is beyond our hearing. In physics, the sound that exceeds 20,000 Hz is called ultrasonic.     3    It does no harm to health.

Sound less than 20 Hz is called infrasonic waves. When we move, the air will vibrate.   4   As the frequency of infrasonic waves is close to that of people’s internal organs⁴, infrasonic wave may cause resonance in human bodies. As a result, people’s vision may weaken and internal organs may rupture. However, whether an infrasonic wave can be used as a weapon depends on its intensity⁵. If its intensity is very low, it won’t damage internal organs or a person’s health.    5    When wind blows at a force of 3 or 4 over the sea6, it will produce infrasonic waves of several decibels. Only typhoons can produce infrasonic waves of over 100 decibels. At present, scientists can only produce infrasonic weapons in the lab with the help of advanced scientific tools and powerful electric power.

词汇：

Immigrant / ˈɪmɪgrənt / vt. 使移居入地

Unique / ʊ"ni:k / adj. 独特的

Scanner / ˈskænə(r) / n. 扫描仪

Disrupt / dɪs"rʌpt / vt. 使中断

Bilingual / ˌbaɪˈlɪŋgwəl / adj. 具备双语能力的

Neuroscientist / "njʊərəʊsaɪəntɪst / n. 神经系统家

注释：

1. an added function：另加的一种功能

2. Once sound exceeds this limit：一旦声音越过了这个界限。 once是时间状语从句的连词。如： Once you have learned how to swim, you will love this sport. 一旦你学会了游泳，你会爱上这一运动的。

3. ear-splitting noise：震耳欲聋的噪音

4. As the frequency of infrasonic waves is close to that of people’s internal organs：由于次声波的频率接近于人体内部器官的频率。 that指代前面的 frequency。

5. However, whether an infrasonic wave can be used as a weapon depends on its intensity：但是，次声波能否用作武器取决于次声波的强度。 whether an infrasonic wave can be used as a weapon是从句，用作句子的主语。

6. When wind blows at a force of 3 or 4 over the sea：当海面上吹起 3～4级风的时候

练习：

A High sound of 150 decibels can kill a healthy rat.

B The vibration of air can produce infrasonic waves.

C We cannot play high-pitched music with ordinary musical instruments.

D If the intensity of infrasonic wave exceeds 160 decibels, it is extremely harmful.

E Dolphins, whales and bats can make such high-frequency sound.

空4

A:A B:B C:C D:D E:E F:F

Why Do People Shrink?