*People solve most life problems for themselves rather than expecting others to care for their needs.
In 1798 the first smallpox vaccine was developed.Over the 18th and 19th centuries,systematic implementation of mass smallpox immunization culminated in its global eradication in 1979.
You could say something along the lines of:
"Hey, Friend, what's so good about weed? Why are you always smoking it?"
If he's smoking it for medical purposes, then just drop it, but if it's illegal and he's doing it to "look cool", then I would further ask questions about it.
From experience with my best friend, I´d say C.