Are you afraid of going to the dentist（牙医）？ If so， you're not alone．

These fears could just be in our heads， however． According to a recent survey by Martin Tickle， a professor at Manchester University in the UK， the pain isn't felt most of the time in dental surgeries（牙科手术）． In fact． among the 451 interviewed patients，75% reported no pain at all during their visits， including situations when they had their teeth pulled out．

Could it be the sound of the drill（钻头）then？

"I found that the sound of drilling can evokedeep worry in dental patients． Actually they don't have any pain． " Hiroyuki Karibe， a scientist at Nippon Dental University in Tokyo， told the Guardian．

To find the reason why a drill might bring on a racing heart， Karibe divided the volunteers into low﹣fear and high﹣fear groups based on how much they feared a trip to the dentist． Volunteers were played the sound of a drill while their brain activities were watched by a machine．

What Karibe found in the low﹣fear group was increased activity in the areas of the brain relative to auditory processing（听觉处理）， which means， for these people， the sound of dental drills is no different from other sounds

In the high﹣fear group， however， the brain area that was activated（激活）was different． It was the area that carries out a number of duties， including learning， feelings and， most importantly， memory． This means that these volunteers not only heard the sound， but they remembered it﹣they made connections between the sound of a drill and the worry it produced in the past， causing their worry to return．

Understanding how brains reply to the sounds of dentists ' drills could help scientists find ways to make patients more relaxed， according to Karibe， because patients who worry about going to the dentist might keep putting off their visits． But the best way is to keep your teeth healthy．

根据短文内容，选择最佳选项，并在答题卡上将选定答案的字母标号涂黑．

（1）How does the writer explain that the pain isn't felt most of the time in dental surgeries？ 　　

A．	By showing facts with numbers．
B．	By asking questions one by one．
C．	By giving examples group by group．
D．	By comparing results of patients．

（2）According to the fourth paragraph， what does the word " evoke" mean in Chinese？ 　　

A．	减轻
B．	引起
C．	显示
D．	阻止

（3）How did the sound of drilling produce different results to the volunteers in the study？ 　　

A．	It produced some worry in the volunteers in the low﹣fear group
B．	For the low﹣fear group， it activated the brain area dealing with learning， feelings and memory
C．	For the high﹣fear group， it caused more activities in the brain area relative to auditory processing．
D．	It made people in the high﹣fear group remember their past uncomfortable memories

（4）What is the last paragraph mainly about？ 　　

A．	How the study might be useful．
B．	Some new ways to treat teeth
C．	The proper way to treat dental patients．
D．	The importance of keeping our teeth healthy．

（5）What's the purpose of the passage？ 　　

A．	To show us different areas of fear in brains．
B．	To introduce us a recent survey by a scientist．
C．	To help us have less fear of a trip to the dentist．
D．	To make it clear that the sound of drilling is not terrible．