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单项选择题

In the fall 2006, the National Basketball Association (NBA) started using basketballs made with synthetic, or manmade material instead of leather. They made the switch because they wanted every basketball they use to feel and bounce the same. However, some players complained right away that the new balls bounced differently and were actually harder to control than leather ones. Dallas Mavericks owner Mark Cuban asked for help the Department of Physics at the University of Texas. The scientists investigated friction that affects the ability of a player to hold onto a ball. "The greater the friction, the better it will stick to his hand", explains Horwitz, one of the physicists who worked on the project. Tests on both wet and dry balls showed that while the plastic ball was easier to grip when dry, it had less friction and became much harder to hold onto when wet. That"s because sweating stays on the surface of the synthetic balls but gets absorbed into the leather balls—an important detail for sweaty athletes. In January, the NBA went back to use the traditional leather balls. They aren"t perfect, but for now, that"s just the way the ball bounces.

When is it harder for an NBA player to hold onto a synthetic ball
A．When sweating sticks to the ball.
B．When the ball is wetted by water.
C．When tests are done on the ball.
D．When the ball is dried with a towel.
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