[单项选择]Addiction is such a harmful behavior, in fact, that evolution should have long ago weeded it out of the population: if it’s hard to drive safely under the influence, imagine trying to run from a saber-toothed tiger or catch a squirrel for lunch. And yet, says Dr. Nora Volkow, director of NIDA and a pioneer in the use of imaging to understand addiction, "the use of drugs has been recorded since the beginning of civilization. Humans in my view will always want to experiment with things to make them feel good. "
That’s because drugs of abuse co-opt the very brain functions that allowed our distant ancestors to survive in a hostile world. Our minds are programmed to pay extra attention to what neurologists call salience--that is, special relevance. Threats, for example, are highly salient, which is why we instinctively try to get away from them. But so are food and sex because they help the individual and the species survive. Drugs of abuse capitalize on th
A. are born with a predisposition to addiction.
B. use certain chemicals long and frequently enough.
C. have sufficient drugs or alcohol to use.
D. create an all consuming pattern of uncontrollable craving.

[单项选择]Addiction is such a harmful behavior, in fact, that evolution should have long ago weeded it out of the population: if it’s hard to drive safely under the influence, imagine trying to run from a saber-toothed tiger or catch a squirrel for lunch. And yet, says Dr. Nora Volkow, director of NIDA and a pioneer in the use of imaging to understand addiction, "the use of drugs has been recorded since the beginning of civilization. Humans in my view will always want to experiment with things to make them feel good. "
That’s because drugs of abuse co-opt the very brain functions that allowed our distant ancestors to survive in a hostile world. Our minds are programmed to pay extra attention to what neurologists call salience--that is, special relevance. Threats, for example, are highly salient, which is why we instinctively try to get away from them. But so are food and sex because they help the individual and the species survive. Drugs of abuse capitalize on th
A. is a very harmful behavior that evolution failed to get rid of.
B. makes it hard for people to drive safely under its influence.
C. has to do with people’s desire to achieve pleasant feelings.
D. is understandable behavior because it dates back long ago.

[填空题]Passive smoking is more harmful to non-smokers than to smokers.

[填空题]In fact, the process of giving up drug addiction for a determined person is easier than what he thought.

[填空题]Due to the fact that light travels______(fast) than sound, lightning is seen before thunder is heard.