Passage One The wheel was one of the man’s first inventions and yet it has also proved one of the most useful. So wide and varied are the uses of wheels, in machines and vehicles of all kinds that it is difficult to imagine what the world would be like without them. It is surprising to hear it said, therefore, that the wheel’s importance will perhaps be greatly reduced by the end of the century by an invention so new as to be still unnamed.The invention is a machine that floats above any surface on a cushion of air. The cushion is formed when air is blown into the bottom of the machine. This part is shaped like a saucer turned upside down. If air is blown into the saucer, the machine rises to a height that may vary from a few inches to a few feet.Industry is already using one form of the invention to deal with heavy loads. It can lift them with ease and since there are no wheels, and therefore no friction, they can be put into motion with the touch of a finger.The new invention, however, is having a great effect on transport. Not only does it make expensive road systems unnecessary, but also it enables vehicles to travel equally well over land or water. This unique ability to reach most destinations has given rise to the prediction that wheeled vehicles may be as uncommon at the end of this century as airplanes were at the beginning of last century.31. The first paragraph tells us that __C___.

A. big wheels have all kinds of uses
B. the wheel’s usefulness hasn’t been proved
C. a new invention may make wheels less important
D. the wheel was man’s earliest invention