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【单选题】
β -OH 蒽醌酸性强于 α-OH 蒽醌, 其原因是( )A.
α-OH 与羰基形成内氢键
B.
α-OH 空间效应大于 β-OH 的空间效应
C.
α-OH 空间效应小于 β-OH 的空间效应
D.
β-OH 形成氢键少于 α-OH 形成氢键
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举一反三
【单选题】The ______ now seems to stand as the primary to a new era of strong economic growth.
A.
defect
B.
descent
C.
deficit
D.
defeat
【单选题】Despite signs Of strong economic recovery, American companies are still pressed for
A.
tremendous debts.
B.
considerable profits.
C.
soaring investment.
D.
excessive growth.
【单选题】The ______ now seems to stand as the primary barrier to a new era of strong economic growth.
A.
defect
B.
descent
C.
deficit
D.
defeat
【单选题】Which of the following may serve as a sign for economic improvement?
A.
Strong consumer spending.
B.
Lower unemployment rates.
C.
The fluctuation of the stocks.
D.
Increased investment in the building industry.
【单选题】The strong tone of US economic recovery is manifested in
A.
the downsizing in manufacturing industries.
B.
the sharp increase in tech-sector production.
C.
the incoming shipments of info-tech goods.
D.
the increasingly wide trade gap in January.
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