intensify: implies a deepening or strenghening of a thing or of its characteristic quality: police ~ied their investigation.


aggravate: implies an increasing in gravity or seriousness of something already bad or undesirable: the problem has been ~d by neglect.


heighten: suggests a lifting above the ordinary or accoustomed: special effects ~ed the sense of terror.


enhance: implies a raising or strengthing above the normal of such qualities as desirability, value, or attractiveness: shrubbery ~d the grounds of the estate.


intensify加强: 泛指加强深化，aggravate恶化: 使(原本不好)更严重，heighten提升: 超越平常普通，enhance提升: 使更理想有价值有吸引力


记忆方法: 1) 首字母HEAI重组成HI你好和EA东亚<==加强关系  四个词中，enhance为褒义，aggravate为贬义，intensify和heighten既可作褒义也可作贬义
   
         2) 加强的意思是加大措施或程度mean to increase markedly in measure or degree.首字母HEAI重组成HI你好和EA东亚<==加强关系