Which of the following is not a step one can take to prevent food borne illnesses?

Since I don't know what the NOT answer is then let's talk about what WILL prevent food borne illness; it will be a process of elimination on your end.

1) proper food storage; refrigerated below a certain degree
2) proper food preparation; not cutting meats & vegetables on same cutting board; cooking meats to right internal temperature
3) proper hand washing of food handlers; wash after using bathroom, wash hands after handling meats; wash hands after handling money before preparing food.
4) keep mouth & nose covered with a mask if have allergies or cold so germs are not spread to food & then to consumers.