. She learnt both business and history, but she knows________of them well, though she can speak on subjects in general.

Remember everybody you meet online is a stranger．So when you can’t see a person, they could be ________．

---Would you like _________to drink?---Yes, please．

(2013·高考重庆卷)Recycling is one way to protect the environment；reusing is________.

I will never know what was on his mind at the time, nor will _______.