Ppf
[医][=pellagra preventive factor]抗糙皮病因子，维生素pp
🗣️ 情景例句
Littering makes the city look like a garbage dump.
随地乱扔垃圾使城市看起来就像个大垃圾堆。
Want of care does us more damage than want of knowledge.
粗心比无知更为有害。
I see.
我明白了。