Teachers say buying homework answers online is not many in schools, but an interview with school students shows only 10% are willing to finish their holiday homework by themselves.
    Their main complaint is that the homework is too much for them to finish.
    “As far as I know, many of my students have to go to all kinds of training classes during the holiday. These take away much of their time for doing homework.”
    But as for the parents  who are sending their children to these training classes  they also say they've got no choice. Here's a view from a student's father.
    "All the other kids in the neighborhood are learning extra things. You know parents sometimes compare their kids. I'm afraid my kid will be less successful than the others in the future."
    In order to do with this situation of students copying each other's homework, some schools have even dropped the idea of holiday homework. Instead, they organize some interesting outdoor activities.
     Educational experts say students love to learn through games or activities that they can be a part of. They suggest schools drop the current (目前的）homework format (设计)，and turn to homework that encourages kids to get involved (参与).This way, they would no longer want to copy from each other or buy answers through the Internet.
    Answer the following questions according to what you read.

    Our ancestors（祖先）made the old saying that friends____(be) like wine-the older,the better.Because of that, many people think old friends to be____(important) than new ones.For example,if two pieces of advice are given to solve a problem,one from a new friend and the other from an old friend,people always prefer to choose the latter one,____the new friend's advice may be better.

    ____(disagree) with the old saying,I believe that new friends are not____(necessary) worse than old friends. Why?Because the____(long) of time cannot tell whether your friendship is better or not.

    Once you call someone friend,he must be a person who is____(rely) and whose interests are in common with____(you).Maybe a friend's outside look____(change) all the time,but the inside characters of him and his interests won't change at all.It is just these unchangeable characters and interests that make him a friend to you.____,there is no difference between old friends and new ones on this point.

①系统地阐述了马克思主义的基本原理

②阐明了共产主义必然代替资本主义的社会发展规律

③揭示了无产阶级的历史使命

④提出阶级斗争在阶级社会中推动历史发展的作用

把盛有水的纸盒放在火焰上烧，水烧开了纸盒仍不会烧着，这是因为（　　）