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如果说某事件具有不确定性，则意味着对于可能的情况无法估计其可能性。在这种情况下，常用定量的方法估计未来投资收益。( )
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More Than 8 Hours Sleep Too Much of a Good Thing Although the dangers of too little sleep are widely known, new research suggests that people who sleep too much may also suffer the consequences. Investigators at the University of California in San Diego found that people who clock up 9 or 10 hours each weeknight appear to have more trouble falling and staying asleep, as well as a number of other sleep problems, than people who sleep 8 hours a night. People who slept only 7 hours each night also said they had more trouble falling asleep and feeling refreshed after a night’s sleep than 8-hour sleepers. These findings, which DL Daniel Kripke reported in the journal Psychosomatic Medicine, demonstrate that people who want to get a good night’s rest may not need to set aside more than 8 hours a night. He added that "it might be a good idea" for people who sleep more than 8 hours each night to consider reducing the amount of time they spend in bed, but cautioned that more research is needed to confirm this. Previous studies have shown the potential dangers of chronic shortages of sleep — for instance, one report demonstrated that people who habitually sleep less than 7 hours each night have a higher risk of dying within a fixed period than people who sleep more. For the current report, Kripke reviewed the responses of 1,004 adults to sleep questionnaires, in which participants indicated how much they slept during the week and whether they experienced any sleep problems. Sleep problems included waking in the middle of the night, arising early in the morning and being unable to fall back to sleep, and having fatigue interfere with day-to-day functioning. Kripke found that people who slept between 9 and 10 hours each night were more likely to report experiencing each sleep problem than people who slept 8 hours. In an interview, Kripke noted that long sleepers may struggle to get rest at night simply because they spend too much time in bed. As evidence, he added that one way to help insomnia is to spend less time in bed. "It stands to reason that if a person spends too long a time in bed, then they’ll spend a higher percentage of time awake." he said. Paragraph 2 ______A. Kripike’s research tool.B. Dangers of habitual shortages of sleep.C. Criticism on Kripke’s report.D. A way of overcoming insomnia.E. Sleep problems of long and short sleepers.F. Classification of sleep problems.
What is the most common form of a trademark
一般来说，标准差越小，各种可能收益的分布就越集中，投资风险也就越小。反之，标准差越大，各种可能收益的分布就越分散，风险就越大。( )
(二) A安装公司承包了某六层商业中心的空调工程，工程内容为空调工程的施工图深化设计、设备材料采购和安装施工。合同规定热泵机组采用国外品牌，工程结算采用工程量清单综合单价计价，工期3个月。合同订立后，A公司编制了空调工程的施工组织设计，热泵机组采用汽车式起重机吊装，该吊装工作分包给B安装公司。B公司依据空调工程的施工组织设计和国家规范标准编制了热泵机组的吊装方案。 工程开工后，因业主装饰设计变更，致使空调工程施工图修改，工程停工数天，影响了计划工期，同时也增加了工程量和新的项目。 问题 B公司在热泵机组的吊装中主要的直接成本是什么？应采取何种措施来控制直接成本？
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