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  3. In fall 2006, the National Basketball Association (NBA) started using basketballs made with synthetic, or man-made, material ins

In fall 2006, the National Basketball Association (NBA) started using basketballs made with synthetic, or man-made, material ins

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问题 In fall 2006, the National Basketball Association (NBA) started using basketballs made with synthetic, or man-made, material instead of leather. They made the change because they wanted every basketball they use to feel and bounce the same. Not all leather balls are exactly alike in weight or how they bounce, but the synthetic balls are.
　　However, some players complained right away that the new balls bounced differently and were actually harder to control than the leather ones.
　　Physics helped answer questions about why the new bails felt different. For example, the scientists studied friction, which in this case affects the ability of a player to hold onto a ball. "The greater the friction, the better it will stick to his hand," explains a scientist.
　　Tests on both wet and dry balls showed that while the synthetic ball was easier to hold onto when dry, it had less friction and became much harder to hold onto when wet. That’s because sweat stays on the surface of the synthetic balls but gets taken into the leather balls.
　　The scientists also tested bounce and found that the logo printed on the new bails made their surface uneven and caused them to bounce a little strangely compared with the leather balls.
　　In January, the NBA went back to using the leather balls. They aren’t perfect, but for now, that’s just the way the ball bounces.
The synthetic ball bounces differently from the leather one mainly because ______.
选项 A、it is wet
B、it is dry
C、there’s a logo on it
D、its weight remains the same
答案C
解析 根据第五段的第一句话的意思：科学家对弹跳力也做了研究，发现贴在球上的商标使得篮球的表面不平，这就使由人工材料制成的篮球和南皮革制成的篮球相比在弹跳的时候有点不同。可很容易选C。
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