—What should I do, doctor?—You should take more exercise ______ healthy.
You can’t believe how terrible the fire is __________ you see it with your own eyes.
Driving in rush hour traffic __________ be very dangerous, so you __________ be too careful.
Jerry is always so busy that he can hardly __________ a few minutes to talk with his child.
---__________ it is from our own planet Earth to Mars!--- Yes, it takes months to travel to Mars by spacecraft.
—Jim took _______ one-hour ride just now. What a short time he spent finishing such a long way!—He is _________ experienced rider.