3. According to the passage, the researchers conducted an experiment on people who are A)employees in Western Electric Co C)patients with lung cancer D)non-smokers 4. In his study Shekelle found A)lung cancer has nothing to do with smoking B)there is correlation between lung cancer and carotene C) preformed vitamin A may protect people against lung cancer D)those who ate the most carotene didn 't develop lung cancer3. According to the passage, the researchers conducted an experiment on people who are ________. A) employees in Western Electric Co B) heavy smokers C) patients with lung cancer D) non-smokers 4. In his study, Shekelle found ________. A) lung cancer has nothing to do with smoking B) there is correlation between lung cancer and carotene C) preformed vitamin A may protect people against lung cancer D) those who ate the most carotene didn’t develop lung cancer