翻译成英语:很少有人说明为什么美国居民变得如此混杂.

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英语专业8级，语法不会有问题的。

1.only a few people tell the reason why american citizens have so much difference.

2.success depends on the extent of our working .

3.it's important for young people to know what should be done,what should not be done.

It is rarely explained why American residents became so mixed up.
Success or not depends on how hard we work.
It is important for us youngsters to know what we should do and not.

1.Few people can explain why US residents are so miscellaneous.
2.Success or not depends on how hard we are working.
3.For young people, the imprortant thing is understand what should do and what should not do.

Very few people could explain why U.S. residents become so mixed

The success or failure depends on the extent of our efforts to work

To our young people,understand what to do and what not to do is important.