A Possible Cause of the Spread of Illness by Food

A possible cause of the spread of illness by food contaminated with Escherichia coli could be

A) a mother who forgets to wash her hands after changing her infant's diaper and then cooks dinner.
B) eating leftover restaurant food that has been stored in the refrigerator for 24 hours.
C) using home-canned green beans to make a green bean casserole for a family meal.
D) keeping a dish containing meat and vegetables warm on a restaurant steam table for an hour.