单选题
Fear can be an effective way to change behavior. One study compared the effects of high-fear and low-fear appeals on changes in attitudes and behaviors related to dental hygiene(卫生). One group of subjects was shown awful pictures of 29 teeth and diseased gums; another group was shown less frightening materials such as plastic teeth, charts, and graphs. Subjects who saw the frightening materials reported more anxiety and a greater 30 to change the way they took care of their teeth than the low-fear group did. But were these reactions actually 31 into better dental hygiene practices? To answer this important question, subjects were called back to the laboratory on two 32 (five days and six weeks after the experiment). They chewed disclosing wafers(牙疾诊断片)that give a red stain to any uncleaned areas of the teeth and thus provided a direct 33 of how well they were really taking care of their teeth. The result showed that the high-fear appeal did actually result in greater and more 34 changes in dental hygiene. That is, the subjects 35 to high-fear warnings brushed their teeth more 36 than did those who saw low-fear warnings. However, to be an effective persuasive device it is very important that the message not be too frightening and that people be given 37 guidelines to help them to reduce the cause of the fear. If this isn't done, they may reduce their anxiety by denying the message or the 38 of the communicator. If that happens. it is unlikely that either attitude or behavior change will occur. A．accustomed B．carefully C．cautiously D．concrete E．credibility F．decayed G．desire I．dimensions I．eligible J．exposed K．indication L．occasions M．permanent N．sensitivity O．translated
【答案解析】空格前的数词two表明此处应填入可数名词的复数形式，词库中的dimensions和occasions符合语法要求。再结合括号中的内容(在实验后的5天和实验后的6周)，可知此处说的是这些研究对象被两度请回了实验室，occasions“时刻，时节”符合句意。而且该词常与介词on搭配，on two occasions意为“两次”。dimensions“方面；维度(如长度、高等)；尺寸，大小”不符合句意，且不能与on搭配。