The correct answer to this question is A, Wash hands with luke-warm water and soap. All water is suitable for different reasons, but when it comes to washing one's hands, warm water is best. It is more effective than cold water at killing germs and bacteria.
Water alone is not enough. Soap, specifically anti-bacterial soap, is essential to use to kill any bacteria that is on one's hands. When it comes to being in a hospital or doctor's office setting, with sick patients, it is essential to wash one's hands to prevent any bacteria or diseases from spreading.