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【简答题】
二级反应2A → B 当A的初始浓度为0.200 mol•L-1 时半衰期为40s,则该反应的速度常数是( ) A. 8 s-1•L•mol-1 B. 0.125s-1•L•mol-1 C. 40 s-1 D. 40 s-1•L•mol-1
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【单选题】I don’t think ___ of his parents are home. They usually go out for a walk at the moment. [ ]
A.
one
B.
any
C.
either
D.
both
【简答题】The sellers are obliged to advise the Buyers of the expected date of shipment and the concrete quantity ready for shipment before the Buyers open letters of credit.
【单选题】下列哪项不是引起B细胞介导的免疫应答水平下降的原因
A.
B细胞表面Fc受体
B.
Th1亚群比值增高
C.
Th2亚群比值增高
D.
特异性循环抗体
E.
抗独特型抗体
【单选题】感染HIV后，下列哪项不是导致机体免疫功能受损的主要机制( )
A.
被感染的CD4+淋巴细胞表面表达gp120，可与其他CD4+细胞相互融合，细胞被破坏
B.
对CD4+淋巴细胞的直接破坏
C.
HIV感染B细胞，能使其大量破坏，抗体生成减少
D.
骨髓干细胞感染HIV，使免疫细胞生成减少
E.
感染HIV后诱发机体的免疫反应，使受感染细胞受到攻击而被破坏
【单选题】—I can't open the top of this apple juice. —______ it.
A.
Mark has to do
B.
Do have Mark to do
C.
Have Mark do
D.
Mark do have
【简答题】We usually think that ______ , but sometimes we ______ for ourselves.
【单选题】Business buyers are heavily influenced by factors in the current and expected economic environment, such as ________.
A.
level of primary demand
B.
organizational objectives
C.
group dynamics
D.
individual motives
E.
culture and customs
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