根据所学化学知识完成下列各小题：
（1）日常生活中用____ 区别硬水和软水，用____ 方法降低水的硬度。
（2）水人类最宝贵的资源。某同学为了净化井水，用纱布、活性炭、石英砂、小卵石等自制了简易净水器，其中活性炭的主要作用是____ 。
（3）“低碳经济”、“低碳生活”的重要含义之一就是节约化石能源，普及利用新能源。人们正在利用和开发其他新能源，如太阳能、____ 等（任写一种）。低碳生活需从细节做起，我的一个低碳举措是____ 。
（4）金刚石和石墨都是由碳元素组成，但金刚石坚硬，而石墨质软，其原因是____ 

    Club sports — for those just like sports

    Many colleges have established many club sports, ____ to meet a special interest or fill a gap ____ an intercollegiate(校际的) team is not available. Some of sports, like fencing, crew and rugby, are sometimes ____ (compete) for club members. They are often played with other colleges and sometimes with community groups. These clubs give you the opportunity ____(play) a sport you love or learn a sport that is new to you. The one drawback(缺点) to club sports is ____ colleges often don't fund(提供资金) them. In these cases, club members have to work hard to organize fund-raisers and collect money to keep their sports ____(go).

    Club sports are less time-consuming ____ other athletic items, and you can easily miss a practice or even a competition if your academic or work commitments are ____(particular) demanding at a certain point. You can also leave a club sport if you find it just isn't working out. However, it's ____ (worthy) it to stick with a club sport for a while.

    Most colleges have a full range of teams, so you can attend sports competitions year-round. At bigger schools, larger sports, like football and basketball, may attract fans from all over the area. ____(small) sports, however, will also attract a group of fans.