需要证明一种中药牙膏对牙周疾病的预防效果，实验设计中不包括
A．人群选择
B．样本含量
C．实验分组
D．空白剂选择
E．历史常规资料分析
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醛固酮分泌增多可使下面哪些血清电解质发生改变（）
A.高Na+
B.高K+
C.低K+
D.低Na+
E.低Cl-
肺热津饬型消渴，若见烦渴不止，小便频数，脉洪数无力，可选方
A．白虎加人参汤
B．消渴方
C．二冬汤
D．玉女煎
E．增液汤
对同一个样品测得8个数据：8.29、8.33、8.38、8.40、8.43、8.46、8.52、8.62（%），试计算该组数据的标准偏差（）
A.0.1056
B.0.11
C.0.0988
D.0.10
| Lichens may grow on the bark of a tree in a steaming tropical rain forest, on the bricks of big city buildings, on rocks in hot springs, on wind-swept mountaintops, and in the driest desserts. In the arctic, they provide the principal food for caribou, and they are one of the few plants that grow in Antarctica. They are pioneers, appearing in barren rocky areas and starting the formation of soil in which mosses, then ferns, and then other plants can take root. Lichens are a partnership of two plants — fungi and algae. The lichen body is made up of a network of fungal strands. In the upper layers of these grow groups of algae. The two organisms live together to the benefit of both, a relationship known as symbiosis. The fungi provide support, absorb water, and shelter the tender algae from direct sunlight. The algae carry on photosynthesis and provide the fungi with food. The algae can live independently and are recognizable as a species that grows alone. The fungi, on the other hand, cannot live apart from their partners. They can be placed in known classes of fungi but are unlike any species that lives independently. So definite are the form, color, and characteristics of these double organisms that for hundreds of years, they were classified as one. More than 15,000 "species" were named. If these organisms are classified as separate species, it is difficult to fit them into the existing system of classification. But if they are classified separately, these species of fungi seem rather strange. Lichens are a splendid example of the difficulties faced by taxonomists in classifying species. |
The word "barren" underlined in Paragraph 1 most probably means _______ .
A．lifeless
B．frigid
C．hard
D．uncovered
某项目经理就一个复杂的问题做了决策，几个月后，类似的问题又出现了，最可能原因是什么？（）
A、风险分析不足
B、疏忽对解决问题的确认
C、忽略了向发起人汇报
D、没有使用鱼骨分析图