Ppf
[医][=pellagra preventive factor]抗糙皮病因子，维生素pp
🗣️ 情景例句
He'll do anything to avoid getting down to math lessons,
他老是设法想逃避数学，
Boy Scouts serve the community.
童子军服务社区。
Yes, I think they'll return next month.
是的，我想他们下个月回来。