In a quiet，darkened lecture room，you begin a frustrating fight against fatigue. The overhead projector hums，and you cannot concentrate on the slides. You stop absorbing information and become absent-minded. The professor lost you a long time ago. You are bored.
Virtually everyone gets bored once in a while. Most of us chalk it up to a dull environment. “The most common way to define boredom in Western culture is‘having nothing to do. ’”says psychologist Stephen Vodanovich of the University of West Florida. And indeed，early research into the effects of boredom focused on people forced to perform. dull tasks，such as working a factory assembly line.
But boredom is not merely an natural property of the circumstances，researchers say. Rather this perception is subjective and rooted in aspects of consciousness. Levels of boredom vary among people：some individuals are far less liable to boredom than others-and some，such as extroverts(性格外向者)，are more likely to have this feeling.
Thus，a new generation of scientists is coping with the psychological interpretations of this most tedious of human emotions-and they have found that it is more complicated than is commonly known. Researchers say that boredom is not a unified concept but rather comes in several flavors. Level of attention，an aspect of conscious awareness，plays an important role in boredom，such that improving a person's ability to focus may therefore decrease boredom. Emotional factors can also contribute to boredom. People who are poor in understanding their own feelings and those who become sucked in and distracted by their moods are more easily bored，for example.
Staying away from tedium is not easy. People who are liable to boredom are more likely to suffer from ills such as depression and drug addiction；they also tend to be socially awkward and poor performers at school or work.
The purpose of the first paragraph is to______.

A. illustrate why people are less able to focus
B. show how boring a lecture in a dark room is
C. tell people how fatigue affects concentration
D. describe a situation where people can get bored