In which scenario is Luis least likely to be successful when it comes to quitting smoking cigarettes?

a) Luis has a strong support system of friends and family who encourage his decision to quit.
b) Luis is using a well-established smoking cessation program and has access to professional help.
c) Luis is attempting to quit without any external support or resources.
d) Luis is aware of the health risks associated with smoking and is motivated to improve his well-being.