Obsessive-compulsive disorder involves both obsessions and
compulsions. Obsessions often include intense worry and fears of
contamination, accidents, or of one's own aggression.
Compulsions are acts repeated to reduce anxiety and commonly
include:
a. cleaning, checking, and counting
b. running, yelling, and hitting
c. yawning, stretching, and smiling
d. travelling, shopping, and breaking the law

Ithink it's choice d (antibiotic resistance)

The answer you're looking for is washing your hands. "at this late date, we all expect our doctors to wash their hands before examining us or performing an operation in order to prevent the spread of infection. surprisingly, physicians did not begin to acknowledge the lifesaving power of this simple act until 1847.it was then that dr. semmelweis began exhorting his fellow physicians at the famed vienna general hospital (allgemeines krankenhaus) to wash up before examining women about to deliver babies. his plea was far more than aesthetic; it was a matter of life and death and to prevent a deadly malady known as “childbed” or puerperal (from the latin words for child and parent) fever."