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。

    It is known that everyone have a dream. I have dreamed of being a doctor since I enter the primary school. With modern life go rapidly nowadays, many people suffer from different kind of diseases, both mentally and physically. As a result, doctors are in great need at home and abroad. My dream is to become successful doctor, helping to save people’s lives. Although to be a good doctor is very difficult, but nowadays I will do whatever I can to keep everyone health. To make ray dream come true, I have told me over and over again that I’ll pay more attention on studies. After all, only by working hardly can one succeed.

已知$a\in R$，则$a=0$是函数$y=x^2+ax+1$为偶函数的（   ）

过氧乙酸是一种常用的消毒剂．现有一种过氧乙酸溶液，其溶质质量分数为15%．请填空：

①100g该溶液中含溶质____g．

②向100g该溶液中加入200g水，所得溶液的溶质质量分数为____．

③将100g该溶液与100g5%的过氧乙酸溶液混合，所得溶液的溶质质量分数为____．

下列函数中是二次函数的有（　　）

①y=x+$\frac{1}{x}$；②y=3（x﹣1）²+2；③y=（x+3）²﹣2x²；④y= $\frac{1}{x^2}$+x．