考博考试

【单选题】
A、wheel is any dish like object that can be used for transportation or in machinery. To be useful, a wheel must revolve (1) an axle, which is normally a shaft attached (2) the wheel’s center.
No one is exactly sure when the wheel was first (3) .But it is thought to have been in use during the earlyBronzeAge in the Tigris-Euphrates Valley in the MiddleEast— (4) Iraq is located today. We know that ancient people there used (5) . These and other wheeled vehicles are shown in artwork from the area (6) back to 3500B、C、
How were such (7) developed The idea began when people placed logs as rollers under a platform. They were used to (8) heavy loads. The center of the logs may have been partly hewn, or carved away, (9) a narrow axle between solid, thick wheels at each enD、Some ancient MiddleEast people even wrapped leather tires around the solid wooden wheels attached to (10) carts.
Probably the first way (11) wheels were used other than for transportation was in pottery making. (12) beautiful and useful pieces of pottery, a potter puts a lump of clay on a horizontally placed wheel which is attached to an axle. (13) the potter sits facing the wheel and makes it spin, using a foot pedal. The potter molds the clay, using both hands (14) fingers, as the wheel spins. Thus the clay is (15) . Various objects (16) bowls, plates, vases, and cups are produced in this manner.
The wheel and axle also have other (17) . They are part of many (18) .An axle attached to a wheel, so that both spin at the same time, permits the use of small amounts of force to (19) very heavy loaD、This wheel-and-axle principle is used in all weight-lifting devices, such as cranes, hoists, and elevators. For example, by pulling a rope wrapped around the rim of a wheel, a person can lift a massive object with only a (20) amount of effort.

A、to B、on C、at D、in
网考网参考答案：A
网考网解析：
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