一列简谐横波在x轴上传播，a、b是x轴上相距S_ab=6m的两个质点，t=0时，b点正好到达最高点，且b点到x轴的距离为4cm，而此时a点恰好经过平衡位置向上运动，已知这列波的频率为25Hz．

智库即智囊集团，又称头脑企业、智囊团或思想库等，是指专门从事开发性研究的咨询研究机构。它将各学科的专家学者聚集起来，运用他们的智慧和才能，为社会经济等领域的发展提供满意方案或优化方案等思想产品，并收取一定费用。据此，以下说法正确的有    （  ）

①思想产品属于商品，因为它是用于交换的劳动产品 

②思想产品不是商品，因为它是“无形”的服务 

③为社会经济等领域提供服务，是智库工作的目的 

④政府应重视智库发展，有利于促进我国自主创新

Dear Abby，

    I'm a helpless mother. My son Tom is 15 years old. I find that the older he grows， the less we talk. I feel very sad and I really need help.

    My first problem is about his hobbies. He spends almost all his spare time on computer games. When he gets home， he always turns on the computer and closes the door. I'm getting worried about him， especially when his English teacher tells me he always gets low marks in the English exams.

    Second， he likes new technology， but I don't have enough money and I can't afford all the things he wants.

    Recently， I've found that he is always alone. I've never seen him talking to his friends on the phone or going out with anyone on weekends. That is the last problem I have.

    What should I do to help him? Please give me some advice.

A helpless mother

******勉励大家，“每个人都有理想和追求，都有自己的梦想。现在，大家都在讨论中国梦，我认为，实现中华民族伟大复兴，就是中华民族近代以来最伟大的梦想。”回首往昔，中华民族摆脱屈辱，终于站起来了，不断追梦始于（    ）