The Daily Patrons of a Local Town Restaurant Became Ill

The daily patrons of a local town restaurant became ill with nausea,vomiting,and diarrhea.Without knowing the cause,which action should be taken immediately to help avoid future problems?

A) Establish a series of cooking classes for all citizens
B) Have a citywide campaign to cover your mouth when sneezing
C) Use bleach to clean the entire restaurant
D) Strongly emphasize the importance of proper hand washing to staff