ANS:C - both (a) & (b)

Work study deals with both (a) & (b): time study and motion study. Time study involves the systematic observation and measurement of the time required to perform a specific task or activity. It aims to analyze and optimize the time required for various work elements involved in a process or operation. Motion study, on the other hand, focuses on the systematic analysis and improvement of the movements and motions performed by workers during task execution. It aims to eliminate unnecessary motions, reduce fatigue, and enhance efficiency by optimizing work methods and ergonomic factors. Both time study and motion study are integral components of work study, which is a systematic approach to improving productivity, efficiency, and quality in work processes. Therefore, the correct answer is both (a) & (b).