Answer:
d. All of the above
Explanation:
In the case where is a large number of manufacturing complexes and if the research is done on productivity so it would be considered as a Hawthorne works that could be possible via partnership done by many industries, universities, etc
There is no correlation between the productivity and the light levels. The speed of an individual workers would be measured the total level of production and the factors impact such as resting periods, working hours etc. It also developed the various kind of positions to represent the productivity that could change in some specific groups i.e. group norms, cohesiveness, etc
So as per the above explanation, the option d is correct