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【简答题】
( 1 )请用氧同位素示踪法写出乙酸与乙醇发生酯化反应的化学方程式 ______________________ 。 能否用氢同位素示踪法揭示酯化反应原理? _______ (选填 “ 能 ” 或 “ 不能 ” ),原因是 ___________________ 。 ( 2 )制取乙酸乙酯反应温度控制在 110-120°C 的目的是 _______________ 。 A. 加快反应 B. 蒸出产物 C. 减少副反应 D. 提高硫酸的脱水性能
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【简答题】经过委员们数次讨论,新的行动方案初见端倪。
【简答题】经过委员们数次讨论,新的行动初见端倪。 Take shape
【单选题】The author implies that the work of Picasso and Braque shifted over the course of their years in that it later came to
A.
render unseen objects in a visible manner, thus permitting access to the subconscious of the visual brain
B.
portray a variety of visual perspectives simultaneously, displaying many sides of an object
C.
abandon and forswear the use of all techniques of lighting and distance in their artwork
D.
consciously apply the law of abstraction to their paintings to illustrate an understanding of the visual brain
E.
critique the brain's ability to mimic by demonstrating the limits of visual representation
【单选题】Since the training course, over 30 employees have exceeded their quotas, ______ previously only around 20 had done so.
A.
despite
B.
whereas
C.
unless
D.
because
【单选题】U 盘加上写保护后 , 对它可以进行的操作是( )。
A.
只能读盘 , 不能写盘
B.
既可读盘 , 又可写盘
C.
只能写盘 , 不能读盘
D.
不能读盘 , 也不能写盘
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