You should be careful of such a person flatters you in your presence and speaks ill of you in behind.
---Let's have a rest, shall we? --- Not now. I don't want to stop _______ the letter yet.
---This physics problem is too difficult. Can you show me __________, Wang Lin? --- Sure.
--- How can I improve my spoken English? --- You have to practise ______ as much as you can.
--- How about going hiking this weekend? --- Sorry. I prefer _______ rather than _______.
The teacher asked the students ________.