I can never forget the days _____ we worked together and the days _____ we spent together.A. when; which B. which; when C. what; that D when; when
The school has developed an online systemstudents can choose their own teachers.
We’d better stay here a little longerhe turns up unexpectedly.
---I’m sorry, but there is no smoking on this flight. ---Oh, I _____that. Sorry, I won’t again.
---Have you read the book? ---Yes. But that one is _____worth reading. I suggest you______ it if you have time.
_____the problem of land erosion getting more serious, the government is searching for a way to deal with it.