材料强度标准值是材料强度概率分布中具有一定保证率的________材料强度值
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永久荷载可用随机变量概率模型来描述，它服从______，一般情况下，其保证率为_______。
A. 正态分布，95%
B. 正态分布，50%
C. 极值I型分布,50%
D. 极值I型分布,95%
可变荷载可用随机过程概率模型来描述，其概率分布服从___________
A. 正态分布
B. 极值I型分布
C. 极值II型分布
D. 极值III型分布
46. What did Harvard scientists do 50 years ago?
A. They raised public awareness of the possible causes of heart disease.
B. They turned public attention away from the health risks of sugar to fat.
C. They placed the sugar industry in the spotlight with their new findings.
D. They conducted large-scale research on the role of sugar in people's health.
47. What does Marion Nestle say about present-day nutrition studies?
A. They took her a full year to track and analyze.
B. Most of them are based on systematic reviews.
C. They depend on funding from the food industries.
D. Nearly all of them serve the purpose of the funders.
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