Which action will prevent this read of infectious diseases?

Eating junk food.
Drinking a lot of soda
Going to school when sick
Washing hands

Can someone plz help me on this?

How is the central idea developed further? (a) the author elaborates on the treatments for allergies in adults and how they work. (b) the author quotes the reactions of experts and the methods used to conduct the study. (c) the author compares the different rates of food allergies shown in children and adults. (d) the author indicates the limitations of the study because of differences in health care.