Time study is a technique used in industrial engineering to determine the time required to complete a specific task or job. It involves observing and recording the activities and movements of workers performing the task in order to establish a standard time for completing the job.

a) Slow worker:
A slow worker refers to an individual who takes a longer time to complete a task compared to the average worker. By conducting a time study on a slow worker, we can identify the specific areas where the worker is taking more time and analyze the reasons behind it. This information can be used to identify areas for improvement and implement strategies to increase the worker's productivity.

b) Fast worker:
A fast worker, on the other hand, refers to an individual who completes a task in less time compared to the average worker. By studying the time taken by a fast worker, we can identify the techniques, skills, or strategies they use to complete the task efficiently. This information can be shared with other workers to improve their productivity and efficiency.

c) Average worker:
The correct answer to the question is an average worker. An average worker represents the typical performance level of workers in a specific job. Conducting a time study on an average worker helps establish a standard time for completing the task, which can be used for planning and scheduling purposes. It also provides a benchmark for evaluating the performance of other workers, identifying areas for improvement, and implementing productivity improvement measures.

d) Apprentice:
An apprentice refers to a worker who is in the initial stages of learning a trade or occupation. Conducting a time study on an apprentice can help assess their progress and determine the time required to complete specific tasks. This information can be useful for setting realistic expectations, providing training and guidance, and monitoring the apprentice's development.

Overall, time studies are essential for analyzing and optimizing work processes, improving productivity, and setting standards for job completion. By studying workers with different performance levels, including slow workers, fast workers, average workers, and apprentices, organizations can gain valuable insights to enhance efficiency and effectiveness in their operations.