阅读短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。
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 canevokedeep 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.