According to the article, which is one of the reasons why legislators have not made summer school compulsory?
A．Students don't like summer school.
B．Instituting such a program would be very expensive.
C．Students who need help the most don't even attend.
D．The program has had mixed results.

未分类题开展集体教学活动需要做哪些准备()

判断题中央银行的主要业务活动没有银行固有办理'存、贷、汇'业务的特征。()

未分类题建构主义的知识观()

未分类题Which of the following is true according to the text?A．Macroeconomics has undertaken evolutionary change.B．Markets may fail due to irrational exuberance.C．Mr. Akerlof won the Nobel Prize for behavioral economics.D．Economic crises occur with different manifestion.

判断题资产组合的方差由各资产的权重和方差决定，与各资产之间的协方差无关。()