1. Math is complex, but it's necessary.

2. Social studies looks simple, but it's informative.
3. Chinese characters is not simple but complex.
4. Technical arts is useful and important.
5. Home economics is both necessary and useful.
6. Fine arts is neither useful nor necessary.
7. Art is not only useful but also necessary.
8. Music looks simple, but it's important and necessary.
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I worte down 8 sentences related to subjects. Would you check unnatural sentences?

In 3, 'Chinese characters are ... '

All the others seem fine.

Sure! I can help you check the sentences and make any necessary corrections.

1. Math is complex, but it is necessary. (This sentence looks fine)
2. Social studies seem simple, but it is informative. (This sentence sounds better if you use "seems" instead of "looks")
3. Chinese characters are not simple, but they are complex. (This sentence is grammatically correct)
4. Technical arts are useful and important. (This sentence is correct)
5. Home economics is both necessary and useful. (This sentence looks fine)
6. Fine arts is neither useful nor necessary. (This sentence is correct)
7. Art is not only useful but also necessary. (This sentence is fine)
8. Music looks simple, but it is important and necessary. (This sentence is correct)

Overall, the sentences look fine with only a minor correction needed in sentence number 2.