小明想验证“用滚动代替滑动可以减小摩擦”的正确性，利用以下一些器材：质量不相等、带钩的木块A和木块B、弹簧测力计、砝码、棉布、圆柱状铅笔若干，进行实验探究．
实验步骤一：把木块A放在水平桌面上，用弹簧测力计拉动木块，记下弹簧测力计的示数F1；
实验步骤二：把____ 放在水平桌面上，将____ 放在其上方，用步骤一的方法拉动木块，记下弹簧测力计的示数F2．
实验分析：当满足____ 的条件时，上述结论是正确的．
下列程序
i=1
WHILE i＜8
i=i+2
s=2*i+3
WEND
PRINT s
END
输出的结果是____．
Jeans have become one piece of clothing worn by the most people in the world. Everybody wears them, from the farmer to the lawyer and from models to housewives. But why have jeans become so popular？You'll get many answers. For some people they look cool, for others jeans are just comfortable. Jeans were first stronger trousers made for farm workers in the states of the American west. In the eastern part of the US jeans were hardly worn at all. They were connected with farm people and the workers. So the rich wouldn't like to wear them. It was James Dean and Marlon Brando that made them popular in movies and everyone started to wear them. They were a symbol of the rebellion of young people during the 1950s and 1960s. So these new trousers were not allowed in American schools and sometimes in theatres and cinemas. As time went on，jeans became more acceptable. American people in Europe and Japan often wore them when they were not on duty to show that they were Americans. The trousers showed the world a happier way of life, something that people needed, especially after what they had gone through in World War II. Jeans had other advantages as well. They didn't need to be washed as often as other trousers and women didn't need to iron them. This became more important as more and more women started working and had less time for housework. Today jeans are an important part of our lives. They are always washed a few times before they are sold to give them a faded look.
