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【单选题】
关系运算中花费时间可能最长的是（ ）A.
选择
B.
投影
C.
笛卡尔积
D.
并
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皮皮学刷刷变学霸
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【判断题】The functions of micronutrients include helping the carbohydrates turn into energy in our cells, providing cushioning and ensuring our cells replicate.
A.
正确
B.
错误
【单选题】The main role of NADPH + H+produced in mature red blood cells is
A.
providing energy
B.
participating in fat synthesis
C.
participating in amino acid synthesis
D.
reducing GSSG to GSH
E.
promoting cholesterol synthesis
【单选题】某营业部有一顾客在办理某项业务时,态度非常蛮横,语言也不文明,并提出了许多不合理的要求,你认为营业员应该如何处理?
A.
坚持耐心细致地给顾客作解释，并最大限度地满足顾客要求
B.
立即向领导汇报
C.
对顾客进行适当的批评教育
D.
不再理睬顾客
【简答题】We wish to obtain first-hand information.
【多选题】Proteoglycans perform many sophisticated functions in addition to providing hydrated space around cells. What are their other functions?
A.
They can form gels of varying pore size and charge density that act as filters to regulate the passage of molecules through the extracellular medium.
B.
They can bind secreted growth factors and other proteins that serve as extracellular signals for cells.
C.
They can block, encourage, or guide cell migration through the matrix.
D.
In all these ways, the matrix components influence the behavior of cells, often the same cells that make the matrix—a reciprocal interaction that has important effects on cell differentiation and the arrangement of cells in a tissue.
【多选题】How do intermediate filaments strengthen cells against mechanical stress?
A.
Intermediate filaments are particularly prominent in the cytoplasm of cells that are subject to mechanical stress.
B.
They are present in large numbers, for example, along the length of nerve cell axons, providing essential internal reinforcement to these extremely long and fine cell extensions.
C.
They are also abundant in muscle cells and in epithelial cells such as those of the skin. In all these cells, intermediate filaments distribute the effects of locally applied forces, thereby keeping cells and their membranes from tearing in response to mechanical shear.
D.
A similar principle is used to strengthen composite materials such as fiberglass or reinforced concrete, in which tension-bearing linear elements such as carbon fibers (in fiberglass) or steel bars (in concrete) are embedded in a space-filling matrix to give the material strength.
【单选题】灌注石膏模型时,为确保模型不出现气泡,应先将少量石膏放于印模何处
A.
上颌腭顶，下颌颊侧
B.
上颌颊侧，下颌舌侧
C.
上颌腭顶，下颌舌侧
D.
上颌颊侧，下颌颊侧
E.
任何位置均可
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