递进关系 moreover，Whatismore，furthermore，then，besides，inaddition，additionally

　　因果关系 because，for，since，as，hencethus，so，consequently

　　转折关系 but，however，onthecontrary，bycontrast，unfortunately

　　让步关系 although，though，eventhough，evenif，nevertheless，nomatter+疑问词

　　条件关系 if，onlyif，ifonly