The factor in the study is the method used.
Option c
Explanation:
Method analysis, a periodical process is the process of studying or understanding how a task or job assigned is done. It details the job or the task.
Here in the given scenario, the manager compares four different methods to do a task. For this, he assigns all the four methods randomly to ten employees thereby he tries to understand the various aspects of all the four methods and the time taken to finish the task using those methods.
This study will help him in figuring out the best method that can be implemented in the job for better results or productivity. Method analysis is basically done for improving or upgrading the efficiency of the method that is used currently.