In a case-control study, the association between obesity and Clostridium difficile was examined. The table below provides the results. Which of the following odds ratios is correct?
Body Mass Index (BMI) Cases Controls
BMI 30 or higher 55 30
BMI less than 25 45 70

a. 0.35
b. 2.85
c. 1.83
d. 0.55