增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1).每处错误及其修改均仅限一词；

2).只允许修改10处，多者（从第11处起）不计分。

Dear friends,

    Do you want to live in a beautifully world? If so, this is our duty to protect the environment.

    We can just started from little things around us. First, we can stick to habit of walking to school instead of take a car or a bus. Second, it's also importance to reuse everything and value our school's environment by picking up rubbish and turning on the lights. Besides, it is necessary what we should protect flowers and trees. And also by growing different plant, we can make our world green. Let's all to take action now and try our best to protect the environment.

Thank you!

我国使用“长征3号甲”运载火箭的动力是由高氯酸铵（NH₄ClO₄）分解所提供的，反应方程式为2 NH₄ClO₄N₂↑+Cl₂↑+4X↑+2O₂↑，则X的化学式为（ ）