You can’t imagine what great trouble they have _____ the problem _____.
Some of the wheat came from Canada. How about ________ ?
Of all the movies I have seen ________ is more memorable than Titanic.
—He has two brothers and three sisters. Do you know ________ of them? —No, I know ________ of them.
—Which share is meant for me? —You can take ________ half. They’re exactly the same.
—Did ________ of your parents come to attend the opening ceremony? — ________ of them came.