Internet is educational . Many people think children should ____to surf the Internet as they wish . In this way ,they can look____ different subjects on different kinds of websites according to their own interest . But in my opinion ,children should always be watched____surfing the internet .

    Many websites have information and pictures that children should not see .There are many things that children don't understand .All of these may have some bad influence on children's ____ Also , it is dangerous to let childern use chat rooms by themselves .Many parents tell their children not to talk to ____on the street , so they should be careful of ____their children talk to on the internet,too . What's ____ sitting in the front of a computer for a long time isn't good for children's eyes , so ____should monitor(监视) the time that children spend on the internet .

    In a word ,children should ____ away from anything that could be bad for them . I ____believe that it is necessary for parents to watch their children when they use internet .

玛雅人的来历从人种学推测应来自(　　)

日积月累。

珊瑚礁（图12所示）主要分布在热带温暖海域，是海洋中重要的生态系统，有“海底雨林”之称。我国海南省沿海均有珊瑚礁分布，东南面积及数量已大幅减少。

简述珊瑚礁的生态功能，并指出其遭受破坏的原因。