class

• "disgusting affair" - Mrs B 


  she is critical of Gerald's "disgusting affair" as a result of its inter-class nature, rather than because of his disloyalty to Sheila.
• "girls of that class" - Mrs B


  This makes it clear that her rejection of Eva's case was purely based on prejudice, shown by Mrs Birlings generalisation "girls of that class". The determiner 'that' demonstrates contempt of the working class ad is further evidence of how deep-rooted the class divide was in 20th century Britain.
• "it wasn't disgusting" - Gerald 


  Gerald refuses Mrs Birling's remark about his relationship with Eva being disgusting. Priestley does this to, perhaps, separate Gerald from the older generation of the characters and their traditional classist views.
• "knew it couldn't last" - Gerald


  This sudden ending of their relationship is evidenced through Gerald dropping Eva like a possession as she "knew it couldn't last", due to her lower-class origins.
• "I wish you hadn't told me" - Sheila 


  It shows how she views herself as the victim, not Eva, and she would rather continue to live in ignorance than be troubled by others' misfortunes. she is the epitome of upper class ignorance.
• "you mustn't try to build up some kind of wall between us and that girl" - Sheila

  The metaphor of "wall" demonstrates the extremity of the separation, and implies there was a physical boundary that kept the lower classes in poverty.
• "You slammed that door in her face" - Inspector 


  Implying the upper classes were deliberate and violent in the ejection of the lower classes. "The door" is a symbol for the systems and establishments that allow the upper classes to exclude or deny the lower classes. E.g. Mrs Birling is able to influence her charity to reject Eva's case.