第7题: [单项选择]单独接触不致癌,在接触致癌物之前或同时接触可增强致癌作用的是 A. 促长剂 B. 启动剂 C. 助癌剂 D. 免疫抑制剂 E. 过氧化物酶体增殖剂 参考答案:C 答案解析:[解析] 有些化合物本身既不具有引发作用,也不具有促长作用,但可以促进引发作用和增强促长作用,即能促进或增强全部致癌过程,故称为助癌剂。而促长剂只在接触致癌物之后才发挥作用。
A. Jim is the second child in his family. B. Jim has a younger sister. C. Jim is the third child in his family. D. Jim is the only child in his family. 参考答案:C 答案解析:[分析] 此题考查获取事实细节的能力。见短文第一句。