Jill Is Eating a Salad at Lunch and Suddenly Feels

Jill is eating a salad at lunch and suddenly feels stomach cramps. She had told the waiter she was allergic to walnuts and he assured her there were none in the salad. Which of the following might have occurred?

A) There were walnuts added to the salad because the cook forgot to exclude them.
B) Although no walnuts were in the salad, there were cashews, and she is reacting to these tree nuts as well.
C) Jill is experiencing an adverse reaction but not an allergic reaction.
D) The salad dressing contained walnut oil.
E) All of the above are possible.