Robots seem very new to most people. But they have a 1 history. A Greek scientist made the first robot. You may 2 robots in some movies. The robots in the movies are usually stronger, faster and 3 than people. In real life, most robots are used in factories. They can do lots of dangerous, difficult or4 jobs. Some people can't look 5 themselves and robots can help them. For example, some people can't see, and they use a guide dog to help themselves move. But now scientists are making a 6 to help them.

    Robots are also used in American hospitals. At one hospital, a robot 7 meals from the kitchen to the sick people's rooms. It never loses its 8 because it has a map of the hospital in its computer system(系统). 9 the future, robots will even work in space. But robots will 10 take the place of(代替)people but only work for people. They can, however, help us in a lot of different ways.

在光滑的水平面上放着甲、乙两辆同样的小车，甲车上放着一个通电螺线管，乙车上放着一块相同质量的条形磁铁，让小车相距一定距离，然后同时放开小车，如图所示，则下列说法中正确的是（　　）

已知a＞0，b＞0，ab=8，则log₂a•log₂（2b）的最大值为 ____

若$a=2^{0.5}$，$b={\log }_{\pi }3$，$c={\log }_2\sin \frac{2\pi }{5}$，则(   )