短文改错。
下面短文中共有10处错误，错误涉及一个单词的增加、删除或修改。
增加：在缺词处加一个漏词符号（∧），并在此符号下面写出该加的词。
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
The students of class 3 had a discussion about if it is necessary to start learning English
from childhood. Some of them think that English learning should start childhood . As little
boys and girls had a good memory, they can learn a lot of English words by the heart .This will
help them laid a solid foundation for their future English learning. But other do not agree.
Young child have to learn Chinese pinyin at school . If they study Chinese pinyin and English at
the same time , it will be very easily for them to mix it up. This will do a lot of harm not only to
their Chinese learning but also to their future English learning. In short, the students have not
arrived in any agreement yet.
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时，不与对颌两个牙保持相互交错接触的牙是（）