题干

【化学选修5】M是一种重要材料的中间体,结构简式为: a=
2
s
t
2
。合成M的一种途径如下:
A~F分别代表一种有机化合物,合成路线中的部分产物及反应条件已略去。
已知:①Y的核磁共振氢谱只有1种峰;
②RCH=CH2  RCH2CH2OH;
③两个羟基连接在同一个碳原子上不稳定,易脱水。请回答下列问题:
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             Parents who help their children with homework may actually be bringing down their school grades. Other forms of prenatal involvement, including volunteering at school and observing a child's class, also fail to help, according to the most recent study on the topic.
The findings challenge a key principle of modern parenting(养育子女) where schools except them to act as partners in their children's education. Previous generations concentrated on getting children to 
school on time, fed, dressed and ready to learn.
       Kaith Robinson, the author of the study, said, "I really don't know if the public is ready for this but there are some ways parents can be 
involved in their kids' education that leads to declines in their academic performance. One of the things that was consistently negative was
 parents' help with homework." Robinson suggested that may be because parents themselves struggle to understand the task." They may 
either not remember the material their kids are studying now, or in some cases never learnt it themselves, but they're still offering advice."
       Robinson assessed parental involvement performance and found one of the most damaging things a parent could do was to punish their children for poor marks. In general, about 20% of parental involvement was positive, about 45% negative and the rest statistically
 insignificant.
      Common sense suggests it was a good thing for parents to get involved because "children with good academic success do have involved
 parents ", admitted Robinson. But he argued that this did not prove parental involvement was the root cause of that success." A big 
surprise was that Asian-American parents whose kids are doing so well in school hardly involved. They took a more reasonable approach, conveying to their children how success at school could improve their lives."