So Xiao Ming and his classmates randomly surveyed 200 people.
(2) The percentage supporting "compulsory smoking cessation" is: 90÷200=45%,
The percentage supporting "warning to quit smoking" is:1-10%-15%-45% = 30%, and the number of people is 200×30%=60 (people).
The number of people who support "drug quitting smoking" is 200× 15%=30 (people).
Supplementary statistics table as shown in the figure:
(3)20000×45%=9000 (person),
Therefore, about 9,000 people in this area support "compulsory smoking cessation";
(4) It is considered that the most effective smoking cessation measure is compulsory smoking cessation.