Answer/ Explanation: n the play "An Inspector Calls" by J.B. Priestley, Mr. Birling refers to Eva Smith as "Miss Birling" when he finds out that she has used the name of his wife, Mrs. Birling.
Mr. Birling mistakenly assumes that Eva Smith has used the name "Mrs. Birling" when she seeks help from the charity organization run by Mrs. Birling. This misconception leads Mr. Birling to refer to Eva Smith as "Miss Birling" during their conversation.
It is worth noting that this is a significant moment in the play, as it highlights Mr. Birling's self-centeredness and lack of empathy towards Eva Smith's situation. The use of the incorrect name reflects Mr. Birling's dismissive attitude towards Eva Smith and his unwillingness to acknowledge her as an individual with her own identity.
Therefore, to answer the question, Mr. Birling calls Eva Smith "Miss Birling" when he mistakenly believes that she has used the name of his wife, Mrs. Birling.