Answer:
Option B, to prevent infection
Step-by-step explanation:
The surface of the skin is home to many microorganisms some of which are pathogenic, or they have the ability to cause infection. This is one of the reasons we have skin -- it provides a physical barrier against entry of these microorganisms that could otherwise cause harm.
Inserting a needle through the skin, however, not only penetrates through this line of defense, but can also thrust the microorganisms on the skin surface into the deeper tissues or into the bloodstream where they can cause infection or sepsis.
Alcohol can denature the proteins integral to the structure of many germs thereby killing them and reducing the risk of infection when a needle is going to puncture the skin. Dead pathogens do not infect the deeper tissues, thus, preventing infection.
The rhyme you may hear is "the more it dries, the more it dies," meaning the longer alcohol dries on the skin surface, the more time it has to denature the proteins of pathogens and kill potentially harmful microorganisms that do not belong in, say, the bloodstream.
So, using an alcohol wipe before a needle puncture is important for the sake of preventing infection, option B.