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分析一个DNA分子时，发现30%的脱氧核苷酸含有腺嘌呤，由此可知该分子中一条链上鸟嘌呤含量的最大值可占此链碱基总数的    (    )

短文改错

假如英语课上老师要求同桌之间交换修改作文，请你修改你同桌的以下作文，文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加，删除或修改。

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 Editor,

    I used to be a physician in the children's department of a hospital. From time to time I treated children who had poisoned by medicine with older family members. The children didn't know the medicine was danger; they just knew it tasted sweet. Children easily open the bottle what we now use in China.

    Some days before I talked about medicines with an American. He showed me a sort of plastic bottle. The design was quite simple and I'm sure our Chinese factories could produce these bottles. The top of the bottle can be opened by pressing down on them while turning, which is difficult for most young children to do so, though grown-up can open these bottles very easily.

    I'm certainly that the expense of making such tops would be very small. As a doctor, I'd love to see this doing. And most parents would be grateful.

Sincerely yours

Li Hua