下述中哪一点不是环境流行病学研究的特点（） A.多因素 B.弱效应 C.非特异性 D

假定甲、乙两只股票最近4年收益率的有关资料如下：

年	甲股票的收益率	乙股票的收益率
2003	5%	10%
2004	8%	9%
2005	12%	6%
2006	7%	11%

　　要求：
　　(1)计算甲、乙两只股票的期望收益率；
　　(2)计算甲、乙两只股票收益率的标准差；
　　(3)计算甲、乙两只股票收益率的标准离差率；
　　(4)假设甲、乙两只股票收益率的相关系数为1，投资者将全部资金按照80%和20%的比例投资购买甲、乙股票构成投资组合，计算该组合的期望收益率和组合的标准差。

信息归纳：阅读下面一份网络上的旅游资料，完成信息表。

Welcome to China     Welcome to China. After you go to Beijing and Shanghai, you could see the differences between them. In some ways they look the same, in some ways they look different. Both of them have tall buildings and wide streets, although some buildings in Shanghai are much taller than those in Beijing. They both are important in China. Beijing is the capital of China; but Shanghai is the biggest city in China. And there are more famous interests in Beijing than those in Shanghai. You can go to the Great Wall, the Palace Museum and so on.     Now they are becoming more and more important in China. And they are famous all over the world.                                                                  Information Card What do the two places both have? 1. They have________. What are the buildings in Shanghai different from those in Beijing? 2. The buildings in Shanghai are ________ those in Beijing. Which city is the capital of China? 3. ________. Which city is the biggest one in China? 4. ________. Are there a lot of interests in Beijing? 5. ________.

Are you going to use _____________ books? [ ]

A. any

B. many

C. some

肝细胞癌患者最具诊断意义的血清学指标是（）

A.碱性磷酸酶

B.酸性磷酸酶

C.CEA

D.POA

E.以上均错误

人体共有（）块骨骼。

A、205

B、206

C、207

D、208