阅读理解。
We redheads are well known for our bad tempers. Now it seems there is scientific backing for our particular
complaining as well.
Scientists in the United States studied a group of 144 dental patients almost half of whom had red hair. They
found that the red-haired group were more sensitive to pain and as a result were twice as likely to avoid visiting
the dentist.
Previous research had shown that redheads were more resistant to the effects of local anaesthesia (局部麻
醉) than people with other hair colours.
The scientists say that this red-haired sensitivity to pain stems from the actions of a gene called MCIR. This
is responsible for the production of melanin which gives skin and hair its colour. In about five percent of white
people the gene is mutated (突变) leading to fair skin and red hair.
Researchers say there are some people with the gene in the brain and that this could affect pain sensitivity.
Professor Daniel Sessler from the Cleveland Clinic in the United States is one of the authors of the study. He
says the research is a considerable scientific breakthrough.
"Red hair is the first phenotype (表现某显性特征的生物个体或群体) of anaesthetic requirement in humans. And what I mean by phenotype is an external (外部的) characteristic."
"So suppose you are walking down the street and you see someone who's a little older and a little younger-
that tells you nothing about their anaesthetic requirement. You see a man and a woman-that tells you nothing
about their anaesthetic requirement. But you see a redhead-aha! You know that person is going to require 20
percent more general anaesthesia."
From my own personal experience I would say that there is some merit to this idea. I have found that I have
had to ask dentists for extra anaesthetic in the middle of procedures.
Some dentists argue that a greater sensitivity to pain might actually benefit redheads and drive them to see
the dentist more quickly. In my own case I can prove that is definitely not true.
1. We learn from the text that red-haired group are ____.
A. easily influenced by the sense of pain and need more anaesthetic requirement
B. usually more sensitive to some painful things
C. just well-known for their good temper and strong pain sensitivity
D. good-looking with fair skin and red hair
2. What do the scientists think this red-haired sensitivity to pain results from?
A. Melanin which is responsible for the production which gives skin and hair its colour.
B. The mutated gene leading to fair skin and red hair.
C. Some persons with this gene in the brain.
D. An external characteristic of a person.
3. According to Professor Daniel Sessler, the most amazing thing about the anaesthetic requirement in humans which can be judged by ____.
A. someone's age and hair
B. someone's gender and figure
C. someone's teeth and the skills of the dentist
D. someone's external characteristic
4. We can infer from the last two paragraphs that ____.
A. redheads need less anaesthetic in the operation
B. the results of this red-haired sensitivity to pain will be the same
C. the writer is a red-haired person
D. redheads have many benefits of being red-haired
（2）v＝
(n=1、２、３、４…)
得α="37° " α+β="90° " 
的速度大小满足一定条件时，粒子先在磁场I区中运动，后在磁场II区中运动，然后又重复前面的运动，直到经过原点O，这样粒子经过n个周期性的运动到过O点，每个周期的运动情况相同，
