—How long are you staying? --I don’t know. _____A. That’s OK. B Never mind. C. It all depends. D. It doesn’t matter.
His _____ expression suggests that the news he read just now must be _____.
It is _____ that Professor Smith will give us a lecture tomorrow.
_______ his research, man can set foot on the moon now.
The rest of the apple _________.
Only when his mother arrived ___________.