1.最高级标志词形容词、副词最高级 most / chief / primary / main / leading / ......
2.唯一级标志词 only / unique / prefer / every / one / of all / perfect / ......
3.因果项标志词 cause / lead to / contribute to / thanks to / owing to / question / answer / why / reason / 其他形式的问句 / ......