如图是探究平面镜成像特点的实验装置图．

阅读材料，回答下列问题。

王亮同学是一位歌迷，下面是他搜集到的歌曲的部分歌词

材料一：我们唱着东方红当家做主站起来，我们讲着春天的故事改革开放富起来，继往开来的领路人带领我们走进新时代……──《走进新时代》

材料二：一九七九年，那是一个春天，有一位老人在中国的南海边画了一个圈，神话般崛起座座城，奇迹般聚起座座金山……──《春天的故事》

请结合所学知识回答下列问题：

2和____能合成4。

如图所示，质量为m=2.0kg的物体置于粗糙水平地面上，用F=20N的水平拉力使它从静止开始运动，t=2.0a时物体的速度达到v=12m/s，此时撤去拉力．求：

语法填空

    Nowadays, it is common that more and more high school students open their own micro blogs on the Internet. For one thing, it can provide a colorful platform to show their talent. For____, it is a useful way ____（release） their pressure. And all these make it more and more popular with high school students. ____ many parents and teachers hold a different view. They think that ____（manage） one's micro blogs will take a lot of time and energy, ____should be used to study．

    In my view, I am in favor____ the activity. Today the Internet is playing an important role in our life. ____, as high school students of the Information Age, we need to learn to make use of this meaningful tool to communicate and display ____（us）.What's more, opening and organizing micro blogs need various abilities such as writing, designing, being skillful at computer and so on. Only if we master those abilities can we make a successful micro blog. ____a result, we improve ourselves while organizing our micro blogs.

    In fact, micro blog itself is of little harm．It is your attitude towards it ____ matters. We should take the advantages and avoid some bad effects.