恩格斯说：“封建的中世纪的终结和现代资本主义纪元的开端，是以一位大人物为标志的，这位人物就是意大利人但丁。”这里的“开端”是指(　　)

    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.

某校共有学生600名，学生上学的方式有乘车、骑车、步行三种. 如图是该校学生乘车、骑车、步行上学人数的扇形统计图，乘车的人数是（     ）

下列关于胡萝卜素的提取实验流程说法正确的是（   ）