You have just finished administering a food/drink questionaire? rest of question below

6. You have just finished administering a food/drink questionnaire to ill and non-ill participants in a Minnesota summer picnic party. The ill individuals developed moderate to severe diarrhea 16 to 46 hours after the picnic. Six persons experienced vomiting. The following data were collected:
ATE DID NOT EAT
Number of people Number of people
Food item Ill Not ill total A.R Ill Not ill total AR RR
Hot dogs 40 30 10 20
Hamburgers 32 8 20 40
Potato salad 45 25 15 25
Ice cream 48 12 2 38
Lemonade 20 40 20 20
N.B: A.R = Attack rate, RR is relative risk
Which food item appears to be the most probable vehicle for the salmonella (agent) infection associated with the illness? [pp. 451-452]
A. Hot dogs
B. Hamburgers
C. Potato salad
D. Ice cream
E. Lemonade