Answer:
A) decline the offer and walk away from the situation, you do not need friends who don't care about your well being. then have a serious chat with them about smoking being bad for them.
B) do not drink alcohol, find something better to do or drink something else, the alcohol may be spiked.
C) decline the offer and talk to that student to tell them to stop. if that doesn't work try to inform an adult without getting the student into too much trouble.
D) tell them no and either keep an eye on them or kick them out. if not talk to them and ask why so that they don't do it again.