文章首段选项标志词：
1． Concept, conception, notion, explanation, core, essence, analysis, justification, definition+of+文章标题
2． What is, what makes, what leads to+文章标题
3． Defy, justify+文章标题
文章末段选项标志词：
effect, impact, consequence, result, summary, conclusion+文章标题
中间段落选项标志词：
1． 所有比较选项：compare, contrast, versus, match, rival, similar, akin to, alien to contrary to,
2． 所有数字选项：data, figure, calculation, census, statistics,
3． 所有百分比选项：percentage, percent, rate, ratio, proportion, density, demography
4． 所有金钱指示选项：salary, wage, income, expenditure, expense, revenue
5． 所有时间集中选项：century, ages, decades, generation, duration, tradition, heritage, process, procedure