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问题 选择题

珊瑚礁之所以能够保持很高的系统生产力，得益于珊瑚虫和藻类的共生，这些藻类靠珊瑚虫排出的废物生活，同时给珊瑚虫提供氧气。通常情况下，失去了共生藻类的珊瑚虫会因为死亡两导致珊瑚礁逐渐“白化”，那里的生物多样性也将锐减，从而造成系统的崩溃。上述现象说明了

①事物内部的各个部分、要素之间是相互联系的

②关键部分的功能及其变化对整体的功能起决定作用

③认识世界要运用综合思维的方式

④系统优化要注意系统内部结构的有序性及优化趋向

A．①②

B．①③

C．②④

D．@④

答案

答案：B

题目分析：①③选项观点正确且符合题意，题中强调珊瑚礁中珊瑚虫和藻类的共生，体现事物内部的各个部分、要素之间是相互联系的，认识世界要运用综合思维的方式，故入选。②④选项观点与题意不符，题中没有强调关键部分的重要性，故没有体现关键部分的功能及其变化对整体的功能起决定作用，题中没有涉及系统内部结构的有序性，故没有体现系统优化要注意系统内部结构的有序性及优化趋向，故排除。

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单项选择题

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 balls 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 balls 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 ball is easier to hold on to ______.

A．when friction is greater

B．when friction is less

C．when it is heavier

D．when it bounces strangely
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