Among the listed options, having a career that has flexible working hours is not a core predictor of happiness at work, unlike having a sense of accomplishment, competence, or matching personal interests. Flexibility contributes positively to work-life balance but does not guarantee overall job satisfaction. The other factors are more closely linked to happiness in the workplace. ;
The option that is NOT a core predictor of happiness at work is having a career that has flexible working hours. While flexibility is beneficial for work-life balance, it does not equate to job satisfaction like accomplishment, matching interests, or a sense of competence does. Therefore, the answer is C.
;