第5题: [单项选择]According to the woman what happened 200 to 500 million years ago A. Some sea creatures developed vertebrae. B. The first giant squid was captured. C. Some sea creatures shed their shells. D. Sea life became more intelligent. 参考答案:C
第15题: [单项选择]最适合于在铀矿工人中研究暴露于氡气与患肺癌危险的研究设计是( ) A. 现场干预试验 B. 病例对照研究 C. 横断面研究 D. 历史性队列研究 参考答案:B 答案解析:[解析] 铀矿工入从暴露于氡气到发生肺癌需要很长的时间,如果用前瞻性研究需要大量的人力、物力和时间,因此用回顾性研究更合适。