If a classmate offers me a cigarette or an alcoholic drink, I will say:"No, thank you. I don't want to smoke/drink because it's bad for my health and it's not good for me."I will:- Politely decline the offer- Explain my reason for declining, if I want to- Look for other activities that don't involve smoking or drinking- Offer support and understanding to classmates who need help quitting smoking or drinking.
because smoking a cigarette and drinking alcohol is bad for my/our health, so declining his offer is much safer.. and i would tell him that it's not good at influencing other people to do such thing.