In this experiment, the famous professor showed three different____ to the study of physics.
— Would you mind my challenging you to a game of chess? — ______.
______ proves that Jack is really enthusiastic and cautious.
Pro. Smith will give us a report to ______ the world present economic problems.
— The water was left running all night long. — It seemed that John ______. He was the last to do some washing.
Your luggage is overweight, so you must decide what to ______.