某发明家的阿姨对他说：“我从来没看到过像你这么游手好闲的男孩……你已经半小时没有说话了，只会打开壶盖再盖上，现在又拿一个咖啡杯和汤匙放在上面观看蒸汽怎么从壶口冒出，并且去盛接及计算有多少水滴。”这位阿姨没有想到，这位发明家的“无聊”举动，竟促成了人类发展史上相当重要的一次转变。这项转变与以下哪项事件有关

    Two men walked through the countryside toward another village. As they come to the edge of a river, they saw an old woman sitting there upset because the bridge was____by the storm, and she was too weak to walk across the stream. The first man said____, “We are tall enough, and we can carry you across” The second man thought it troublesome, but he agreed reluctantly（不情愿地）. So the two men ____ the bridge, lifted her between them and carried her across the river. When they got to the other side, they set her down and she went on her way gratefully. After they had walked another mile or so, the second man began to complain “My back began to hurt for lifting her.” The first man ____ smiled and nodded without a word.

关于北纬30°纬线的说法，错误的是（  ）