Usages of yuányīn
他 不 复习 的 原因 是 太 累 了， 结果 考试 没 考好。tā bú fùxí de yuányīn shì tài lèi le, jiéguǒ kǎoshì méi kǎohǎo.
The reason he didn’t review was that he was too tired, and as a result he didn’t do well on the exam.
空气 污染 这么 严重， 一 个 原因 是 塑料 垃圾 太 多。kōngqì wūrǎn zhème yánzhòng, yì gè yuányīn shì sùliào lājī tài duō.
For air pollution to be this serious, one reason is that there is too much plastic trash.
猜 一下 原因。cāi yíxià yuányīn.
Guess the reason.
这 是 真正 的 原因。zhè shì zhēnzhèng de yuányīn.
This is the real reason.
我们 需要 调查 原因。wǒmen xūyào diàochá yuányīn.
We need to investigate the reason.
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