Ppf
[医][=pellagra preventive factor]抗糙皮病因子，维生素pp
🗣️ 情景例句
Live and let live.
各人有各人的活法。
Where will you be nest year at this time?
明年这个时候你将在哪里？
We enjoy staring at them, entranced as they go about their business, unaware (we hope) of our presence.
我们喜欢入迷地看它们做事，它们不知道（但愿如此）我们就在它们身边。