The term "Scandinavian-Americans" was used incorrectly to refer to a typical food of Americans of Norwegian descent. This is because lutefisk is a typical Norwegian food that is a Nordic country, and it is incorrect to use the word "Scandinavian" to refer to a Nordic country.
The answer is 'by not fulfilling expectations'. The other options don't really surprise the reader, and if the plot is going into one direction, and then what you'd expect to happen doesn't actually happen, you are surprised, and the element of irony is achieved.
