The answer to this question would be: c. is no more effective than any other available treatment.
Hypnosis is one of the treatments that suggested by many people. But the effectivity is highly varied in a different person, so it doesn't work same for every person. Some people even can't be hypnotized. It is hard to be validated so it has a high chance for someone to do fraud without known.
Nowadays, there is not enough evidence to support hypnosis to be used as smoking cessation.