Mr.Green didn’t understand ________ made his daughter so absent-minded this morning.
These old pictures bring to their mind the college days ________ they spent together, ________ life was hard but happy.
_____ leaves the room last ought to turn off the lights.
You can’t imagine ______ when they received these nice Christmas presents.
My new pen ______. Who ______ have taken it?
— David hasn’t come yet.—I think he will ______ soon, for he means what he says.