Ppf
[医][=pellagra preventive factor]抗糙皮病因子，维生素pp
🗣️ 情景例句
What makes you work so hard?
什么使你这样卖命？
I suppose so.
我想是这样。
Just as Mrs.Richards was entering the dinning room, there was a knock on the front door.
理查兹夫人刚刚走进餐厅，前门就传来敲门声。