Ppf
[医][=pellagra preventive factor]抗糙皮病因子，维生素pp
🗣️ 情景例句
I'd like to check this book out.
我想借这本书。
I'm taking Chinese and History.
我将选中文和历史。
It is bacteria that have generated the oxygen we breathe on earth.
正是细菌生产出我们在地球上呼吸的氧气。