—Kathy and her sister are so alike.—I can’t tell one from ____.
— Do you know where David is? I couldn’t find him anywhere. — Well. He ________ have gone far — his coat is still here.
Sara hopes to become a friend of _________ shares her interests.
He has some doubt ________ he will succeed in his research work.
_________ is known to all, the moon travels round the earth once every month.
Sorry, I am late. I ______ have turn off the alarm clock and gone back to sleep again.