Question

what is not a recommended way of quitting smoking?
taking prescription medicine
quitting all at once
switching to low - tar cigarettes
chewing nicotine gum

Explanation:

Taking prescription medicine (under medical supervision), quitting all at once (for some people), and chewing nicotine gum are common recommended ways to quit smoking. However, switching to low - tar cigarettes is not a recommended way. Low - tar cigarettes still expose the smoker to harmful chemicals and nicotine, and may give a false sense of safety while not actually helping in quitting.

Answer:

switching to low - tar cigarettes