Find ONE mistake in each of the following sentences and correct it

giúp mình bài này với mình đag cần gấp:
Find ONE mistake in each of the following sentences and correct it.
1.English is easier Chinese.
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2.China's popullation is more bigger than Japan's.
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3.She is more happy today than she was yesterday.
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4.She is much intelligent than her brother.
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5.This car is badder than that one.
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Cảm ơn mọi người nhìu nha!!!!!!!!!!!!!!!!