Passage Two

　　Man‘s first real invention， and one of the most important inventions in history， was the wheel. All transportation and every machine in the world depend on it. The wheel is the simplest yet perhaps the most remarkable of all inventions， because there are no wheels in nature—no living thing was ever created with wheels. How， then， did man come to invent the wheel? Perhaps some early hunters found that they could roll the carcass of a heavy animal through the forest on logs more easily than they could carry it. However， the logs themselves weighed a lot.

　　It must have taken a great prehistoric thinker to imagine two thin slices of log connected， at their centers by a string stick. This would roll along just as the logs did， yet be much lighter and easier to handle. Thus the wheel and axle came into being and with them the first carts.

　　66. The wheel is important because _______.

　　A. it was man‘s first real invention B. all transportation depends on it

　　C. every machine depends on it D. both B and C

　　67. The wheel is called _______.

　　A. simple B. complicated C. strange D. unusual

　　68. It was remarkable of man to invent the wheel because _______.

　　A. it led to many other inventions B. man had no use for it then

　　C. there were no wheels in nature D. all of the above

　　69. The wheel was probably invented by ______.

　　A. a group of early hunters B. the first men on earth

　　C. a great prehistoric thinker D. the man who made the first cart

　　70. This selection says that the first wheel may have been a ______.

　　A. round piece of stone B. heavy log C. piece of metal D. slice of log