Final answer:
In the context of the research on the effect of lighting on job performance, lighting is the independent variable, as it is the factor being manipulated in the study.
Step-by-step explanation:
The study investigates the effect of lighting on an individual's job performance. The independent variable in this research is the factor that the experimenter manipulates to observe its effect on another variable. Therefore, the independent variable for this study would be (b) Lighting, since it's the element that is being changed to assess its impact on job performance, which in this case would be the dependent variable.