Imagine one day reading that you had been a subject in a risky science experiment without knowing it. At school, you had been fe

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问题     Imagine one day reading that you had been a subject in a risky science experiment without knowing it. At school, you had been fed cereal laced with radioactive chemicals so scientists could learn more about the digestive system. Because the food was radioactive, scientists could easily trace its path through the body.
    Scientists now know that exposure to large amount of radiation can cause cancer, a group of diseases in which bodily cells grow wildly out of control. Some people who were part of the radiation studies later developed cancer and blamed the radiation for causing the cancer. Others are worried the radiation will some day make them sick.
    Some doctors say that, in many cases, such fears are unjustified because the radiation doses used in the experiments were too small to cause harm. They also say that since dangers of radiation were less well understood then than they are now, even researchers who used high doses of radiation didn’ t do anything wrong.
    Some critics claim that no excuse is acceptable for not informing subjects about the nature of an experiment and giving them a chance to refuse to participate. Today, government rules require such informed agreement whenever a study uses people.
The word "laced" in paragraph 1 most likely means______.

选项 A、confused
B、surrounded
C、mixed
D、covered

答案C

解析 本题为词义推测题。由定位句可知,科学家为了做试验,在谷类食物中放人放射性化学物质。mixed意为“混合的,掺杂的”,最符合题意。故选C。
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