Ppf
[医][=pellagra preventive factor]抗糙皮病因子，维生素pp
🗣️ 情景例句
I know.
我知道。
His heart cannot be pure whose tongue is not clear.
嘴不净者心不纯。
Then he said something and I understood it.
接着，他说了点什么，这回我听懂了。