Mr. Smith found that gas from the pipe when he came back because we forgot to switch off. But at last we were lucky to escape .
Mr.Smith was much surprised to find the watch he had had _______was nowhere to be seen.
Only when class began _______that he had left his book at home.
The students in this college are all taking courses _______a degree.
----You can’t finish the book in less than an hour, I suppose? -----________.
They said good-bye, little knowing that they_______ again.