  A said: In the set {B} there are an even number of knights.  B said: In the set {A,C} there are an odd number of knights.  C said: In the set {A,B,D} there are an odd number of knights. 
  Then D said one of the following three statements:   In the set {A,B} there are an even number of knights.  In the set {A,C} there are an odd number of knights.  In the set {A,B} there are an odd number of knights. 

  Who is a knight and who is a knave? 

