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【简答题】
化合物A在薄层板上从样品原点迁移8.2cm,溶剂前沿迁移至A斑点以上4.8cm处。 (1)计算A的Rf值。 (2)若溶剂前沿移动至样品原点以上15.6cm,A斑点应在此薄层板上何处?
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【多选题】以下对总效用和边际效用关系表述正确的是( )
A.
MU 小于零时，TU递减；
B.
MU 大于零时，TU递增；
C.
MU 大于零时，TU递减；
D.
MU 等于零时，TU达到最大值；
【单选题】People all over the world ______.
A.
wonder what to do in the future
B.
pay no attention to the UN's call
C.
take no measure in conservation
D.
should act quickly to answer the UN's call
【多选题】以下对总效用和边际效用关系表述正确的是
A.
MU小于零时，TU递减
B.
MU大于零时，TU递增
C.
MU大于零时，TU递减
D.
MU等于零时，TU达到最大值
E.
MU等于零时，TU达到最小值
【单选题】听力原文：M: Do you know where Mr. Brown is? W: He's in with the manager. M: I wonder what they are talking about. W: The next stage of the project, I think. Who are the two speakers?
A.
Mr. Brown' s colleagues.
B.
Mr. Brown' s workers.
C.
Mr. Brown' s students.
【简答题】完形填空 When your kids were six or seven, you sent them to school. Did you ever wonder what goes through a teacher's 1 as he or she tries to teach your kids? Did you ever wonder what the teacher 2 from y...
【简答题】以下对总效用和边际效用关系表述正确的是( )A. MU小于零时,TU递减; B. MU大于零时,TU递增; C. MU大于零时,TU递减; D. MU等于零时,TU达到最大值; E. MU等于零时,TU达到最小值。
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